Introduction to SET50 Index Options
What is an Option?
An option is a contract which provides the buyer with the right to buy or sell an asset in the future at the predetermined price and quantity. The option seller is the party that sells the right to the option buyer. An option contract has the following characteristics:
 The option buyer has the right to choose whether or not to exercise the option contract.
 If the option buyer chooses to exercise the option contract, the option seller has an obligation to follow the contractual agreement.
 On the day the contract is bought, the option buyer must pay the seller an amount of money called the “Premium”.
Options are classified into two classes according to their rights:
 Call Option
A call option is a contract that provides the buyer with the right to buy the underlying asset (long call) at a quantity and price specified in the contract. The call option seller has an obligation to sell the underlying asset (short call) to the call option buyer.
 Put Option
A put option is a contract that gives the buyer the right to sell the underlying asset (long put) at a quantity and price specified in the contract. The put option seller has an obligation to buy the underlying asset (short put) from the put option buyer.

Call Options

Put Options

Long Position 
Right to buy 
Right to sell 
Short Position 
Obligation to sell when the option is exercised 
Obligation to buy when the option is exercised 
The first option traded on the TFEX is for SET50 Index. The SET50 Index Options are Europeanstyle. The buyer has the right to buy or sell the SET50 Index from/to the seller at the specified exercise price (normally noted as X or K) and other contract conditions, as specified in the contract (both put and call options for the TFEX). Currently SET50 Index is still the only underlying asset traded in the options market.
Profit/Loss from an option
As the buyer will exercise the option only when there is some profit to be made from exercising, the maximum loss of the option buyer is equal to the premium. On the other hand, the maximum possible profit of the option seller is also equal to the premium (commission fee exclusive).
If the price of the underlying asset increases, the call option buyer—who has the right to buy the underlying asset at the specific price—can potentially profit massively (depending on how far the underlying asset rises in price). That means the call option seller is exposed to a loss of an equal amount. On the other hand, when the price of the underlying asset falls, the put option buyer—who has the right to sell the underlying asset at a specified price—can profit until the price of the underlying hits zero (it can’t get any cheaper). At this point, the put option buyer would have made the maximum profit—equal to the strike price minus the premium; the put option seller's maximum loss would be equal to the strike price minus the premium.
The conclusions are as follow:

Maximum profit 
Maximum loss 
Long Call 
Unlimited 
Limited = Premium 
Short Call 
Limited = Premium 
Unlimited 
Long Put 
Limited = Strike  Premium 
Limited = Premium 
Short Put 
Limited = Premium 
Limited = Strike  Premium 
BreakEven Point

Breakeven point 
Long Call 
Strike + Premium 
Short Call 
Strike + Premium 
Long Put 
Strike  Premium 
Short Put 
Strike  Premium 
Profit/Loss Chart
An Option’s Moneyness
The moneyness of an option is its intrinsic value—that is, the value the option would have if exercised immediately. The three types of options moneyness are as follow:
 IntheMoney (ITM)—positive intrinsic value.
 A Call option with an exercise price (Strike) of Bt250 when the current price of the underlying asset (Spot) equals Bt300 (intrinsic = 300 – 250 = Bt50).
 A Put option with an exercise price of Bt300 (Strike) when the current price of the underlying asset (Spot) equals Bt280 (intrinsic = 300 – 280 = Bt20).
 OutoftheMoney (OTM)—negative intrinsic value.
 A Call option with an exercise price (Strike) of Bt270 when the current price of the underlying asset (Spot) equal Bt 200 (intrinsic = 200 – 270 = Bt 50).
 A Put option with an exercise price (Strike) of Bt260 when the current price of the underlying asset (Spot) equals Bt290 (intrinsic = 260 – 290 = Bt 30)
 AttheMoney (ATM)—has an intrinsic value of zero.

Strike < Spot 
Strike = Spot 
Strike > Spot 
Call 
OTM 
ATM 
OTM 
Put 
ITM 
ATM 
ITM 
Characteristics and Specifications of SET50 Index Options
TFEX has specified the characteristics for SET50 Index Options as follow:
Underlying Asset
The underlying asset of a SET50 Index Option is the SET50 Index. The index value is calculated from the market value of the top 50 stocks compiled and announced by the Stock Exchange of Thailand. The calculation used is the Market Capitalization Weight Method.
Contract Multiplier
The contract multiplier of a SET50 Index Option is equal to Bt 200 per 1 index point. That means if the index trades at 300 points, the value of the contract will be 300 x 200 = Bt60,000.
Contract Months
The TFEX has set the contract months (expiry months) of SET50 Index Options as the last month of each quarter—March, June, September and December. For example, if today is 24 Nov, 2008 the outstanding option contracts being traded will be for the following contract months only:
 December 2008
 March 2009
 June 2009
 September 2009
However, on the last trading day of the nearest contract, a new further contract will be opened for trading. Assuming that today is the last trading day for the contracts expiring in Dec 2008, a new contract expiring in Dec 2009 will automatically be opened for trading.
Tick size
The tick size for a SET50 Index Options equals 0.1 of an index point. That means that the price difference between each order cannot be less than 0.1.
 Examples of valid price ranges are 5 points, 5.1 points and 5.5 points.
 Examples of invalid price ranges are 5.11 points, 5.25 points and 5.99 points.
Ceiling/Floor
The TFEX has set a daily ceiling and floor for SET50 Index Options. The ceiling is 30% above the previous day’s settlement price; the floor is 30% below the previous day’s settlement price. In addition, the lowest price cannot be less than 0.10 of an index point.
Example:
Types of Options
There are two types of options, differentiated by whether there is right to preexercise:
 A European option can be exercised only on the expiration date.
 An American option can be exercised at any time prior to or on the expiration date.
All SET50 Index Options currently traded are European.
Exercise Price/Strike Price
The spread of the exercise prices specified by the TFEX are equal to 10 index points. That means each strike price differs by a minimum of 10 points and the unit number is always 0, such as 280 290 300 310 and 320 etc.
In addition, there are always eleven option contracts at the beginning of every trading day, regardless of the contract month. They comprise:
 AttheMoney (ATM), or the contract with a strike price as closest to ATM (one contract).
 Inthemoney (ITM) and Outofthemoney (OTM) contracts (not less than five contracts of each).
Assuming that the strike price closest to ATM is equal to 300 index points, the contract expiring in December 2009 (Z09) consists, at a minimum, of the following contracts:
Call Options 
Put Options 
S50Z09C250 
S50Z09C260 
S50Z09C270 
S50Z09C280 
S50Z09P250 
S50Z09P260 
S50Z09P270 
S50Z09P280 
S50Z09C290 
S50Z09C300 
S50Z09C310 
S50Z09C320 
S50Z09P290 
S50Z09P300 
S50Z09P310 
S50Z09P320 
S50Z09C330 
S50Z09C340 
S50Z09C350 

S50Z09P330 
S50Z09P340 
S50Z09P350 

Trading Hours
The trading day is divided into four sessions
Session 
Details 
Period 
1 
Preopen 
9:15 – 9:45 
2 
Morning session 
9:45 – 12:30 
3 
Preopen 
14:00 – 14:30 
4 
Afternoon session 
14:30 – 16:55 
Last Trading Day
The last trading day of each contract is the day prior to the final exchange business day in the contract month. Examples are as follows:
Expiration MonthØ 
Last trading day 
December 2008 
29 December 2008 
March 2009 
30 March 2009 
June 2009 
29 June 2009 
September 2009 
29 September 2009 
December 2009 
29 December 2009 
In addition, on every final trading day, the contract can be traded until 16.30 hrs.
Final Settlement Price
The price comes from the average value of SET50 Index on the last trading day of the option contract. It is calculated from the SET50 index on a minutebyminute basis during the last 15 minutes before trading ends, starting from 16:15 hrs through to 16:30 hrs, and the close value of the index on that day. The 3 highest and 3 lowest values are excluded from the sample and two decimal points are used for rounding the number to an average.
Cash Settlement
For the sake of convenience, there is no physical delivery of an option contract of the SET50 Index. Only cash settlement is made. The gains and losses from the contract’s position will result in a cash transfer to the customer’s account. When a contract is settled in cash, its position is declared closed.
Contract Code
Single Order
The contract code for a single order for a SET50 Index Option comprises the five parts shown below.
Part 1 
Part 2 
Part 3 
Part 4 
Part 5 
S50 
Z 
09 
C 
300 
Part 1: Underlying Asset
The SET50 index is the only underlying asset for an index option. S50 is used as its symbol.
Part 2: Contract Month
The symbol of each expiry month is represented by a letter, see below.
Contract Months 
Symbol 
March 
H 
June 
M 
September 
U 
December 
Z 
Part 3: Expiry Year
The last two digits of the expiry year are used—such as 08 for the contract expiry
year 2008 and 09 for a contract due to expire in 2009.
The contract codes of SET50 Index Options for all contract months can be found in Attachment 1
Part 4: Types of Rights
C stands for a Call option and P for a Put option.
Part 5: Exercise/Strike Price
Examples of contract codes for SET50 Index Options using Single Orders
Combination Order
A Combination Order is not yet available for an option contract.
Circuit Breaker
Circuit Breaker of TFEX will be in line with that of SET. Therefore whenever the SET closes due to a circuit breaker, the TFEX will also close for trading.
Circuit Breaker conditions specified by SET are as follow:
The first Circuit Breaker kicks in when the SET Index declines 10% from its previous day’s closing price. The SET stops trading for 30 minutes.
The second Circuit Breaker is engaged when the SET Index falls 20% from its closing price on the previous trading day. The SET stops trading for one hour.
After the second Circuit Breaker has kicked in and then one hour has elapsed, the SET reopens for trading until normal closing time without any further stops. In cases where the remaining trading time of the session is less than 30 minutes or 1 hour when the Circuit Breaker engages, the SET will stop trading during that remaining time only.
Opening and closing Positions
When trading options for the first time, an investor must specify whether to buy open or to sell open the position. Examples of the two actions are explained below:
BuyOpen a Call Option
After an investor buyopens a call option, he can choose to close out the position before the contract expires by sellclosing the same series contract. Examples follow:
 An investor buyopens call options of the SET50 Index at a strike of 300 index points expiring in Dec 2010 for two contracts with a premium of 10.0 index points
The commission fee for options trading equals Bt90 per contract, plus VAT 7%, so the buy open order of S50Z10C300 for two contracts at 10.0 points will cost the investor:
 premium 2 x 10.0 x 200 = Bt4,000
 commission fee and VAT 2 x Bt90 x 1.07 = Bt 192.60
 The investor decides to close out the two call positions. By that time, S50Z10C300 has a premium equal to 17.0 index points. Therefore the investor sends an order to sellclose S50Z10C300 for two contracts. The investor is entitled to:
 receipt of premium 2 x 17.0 x 200 = Bt 6,800
 profit = 6,800 – 4,000 – (2 x 192.60) = Bt2,414.80 (ignore the costofcarry)
However, he also has to pay:
commission fee and VAT 2 x Bt90 x 1.07 = Bt 192.60
SellOpen a Put Option
After an investor sellopens a put option, he can choose to closeout the position before the contract expires by buyclosing a put option with the same contract conditions as the one he opened. For example:
 An investor sellopens put options of the SET50 Index at a strike of 250 index points expiring in September 2011 for three contracts with a premium 10.1 index points. If the commission fee for options trading equals Bt90 per contract, plus VAT of 7%, sending a sellopen order of S50U11P250 for three contracts at 10.1 points will mean the following transactions for the investor:
 receipt of premium 3 x 10.1 x 200 = Bt6,060 (initial margin is required)
 payment of the commission fee and VAT 3 x Bt90 x 1.07 = Bt 288.90
 The investor decides to closeout the three sell positions. By that time,
S50U11P250 has premium equal to 8.3 points. Therefore the investor sends an order to
Buyclose S50U11P250 for three contracts. This creates the following transactions for the
Investor:
 payment for premium 3 x 8.3 x 200 = Bt4,980
 payment for commission and VAT 3 x Bt90 x 1.07 = Bt288.90
 receipt of profit = 6,060 – 4,980 – (2 x 288.90) = Bt1,368.90 (ignore cost of carry)
The transactions occurred as a result of the above actions are summarized in the below table.

Buyopen an option 
Sellclose an option 
Cash Received/Paid 
 Pay premium
 Pay commission fee
 Pay VAT

 Receive Premium
 Pay commission fee
 Pay VAT

Initial Margin 
 Not required for BuyOnly position


Contract Holding Till Expiration Once the contract expires, the system will use the final settlement price to check the levels of strike prices that are viable to exercise automatically from remaining long positions. Profits less exercise fee will be added to the equity balance of long position holders, while losses will be deducted from the short position issuers (no fee applied).
Example of Profit and Loss Calculation on Expiration
Investor A bought while Investor B sold 2 S50Z09C300. On the expiration, the final settlement price is 323.01 point. The exercise fee is Bt10 per contract and VAT is 7%.
Investor A gains profit = 2 x {(323.01 – 300) x 200 – (10 x 1.07)} = Bt9,182.60 (added to the equity balance).
Investor B losses = 2 x {(300 – 323.01) x 200} = Bt9,204 (deducted from the equity balance)
Remark: If investors do not want to exercise the options for any reason, they can give instructions to cancel the automatic exercising to the account officer. For online investors, the auto exercise cancellation instruction can be selfentered into the system.
Caution: Normally, the system will not exercise outofthemoney options. If an investor overrides the criteria either intentionally or mistakenly, he or she has to bear the incurred loss. Therefore, to send an overriding instruction should be done only when the final settlement price is known at 17.45 hours on the last trading day.
Example

Investor A 
Investor B 
Position 
Buy call options S50Z09C300 
Sell call options S50Z09C300 
Number of contract 
2 contracts 
2 contracts 
Final Settlement Price 
323.01 points 

Exercising fee 
Bt 10 per contract 
Bt 0 per contract 
VAT (7%) 
10 x 0.07 = Bt 0.7 per contract 
Bt 0 per contract 
Profit / loss 
2 x [(323.01 – 300) x 200 –(10 + 0.7)] = Bt 9,182.60 
2 x [(300 – 323.01) x 200= Bt 9,204 
Conclusion: Investor A gains (equity balance increase) and investor B loses (equity balance decrease)
Speculative Position Limit
The maximum number of contracts that a speculator may hold in SET50 Index Options (calculated as delta equivalent to the position of SET50 Index Futures) is not more than 20,000 contracts on one side of the market in any contract month or all contract months combined.
Reportable Limit
As specified by the SEC and TFEX, all brokers must report name lists of clients that hold at least 500 contracts or equivalent in SET50 Index Futures and/or SET50 Index Options in any contract month or all contract months combined. The contract will be computed from one single contract month and net of all contract months. However, investors can still increase net holding positions so long as they do not exceed their authorized credit limits and do not exceed the speculative position limit set by the TFEX.
Commission fee and Brokerage fee
Commission fee
The commission fees for SET50 Index Options are specified by the TFEX as a sliding scale based on the number of contracts (VAT exclusive) traded in a day. The fees for offline and Internet trading are as follows:
Examples
 An investor buys 1 contract of S50Z11C700 via offline trading so the commission fee (VAT exclusive) is equal to Bt85
 An investor buys 1 contract of S50Z11C700 via Internet trading so the commission fee (VAT exclusive) is equal to Bt77.
 An investor buys 50 contracts of S50Z11C700 via offline trading so the commission fee
(VAT exclusive) is equal to 65 x 50 = Bt3,250.
 An investor buys 50 contracts of S50Z11C700 via Internet trading so the commission fee
(VAT exclusive) is equal to 59 x 50 = Bt2,950.
 An investor buys 150 contracts of S50Z11C700 via offline trading so the commission fee
(VAT exclusive) is equal to 45 x 150 = Bt6,750.
 An investor buys 150 contracts of S50Z11C700 via Internet trading so the commission fee
(VAT exclusive) is equal to 41 x 150 = Bt6,150.
Brokerage fee
Service Type 
Fee(Bt/contract)

Exercise 
10 
Deny 
10 
Assign 
none 
The above brokerage fee is VAT exclusive. In the case of AutoExercise, the fee collected does not exceed the exercising value.
