You just got off the plane and as you reach to pick up your bags at the Bangkok International Airport, a well mannered Thai reaches over with a bag cart to assist you. After he helps you put the bags into the taxi, you reach into your wallet to tip him. "How much?" you ask and he answers, "It's up to you."
Checking into your hotel, the bell boy assists you with your baggage. In your room, he places your suitcases on the table, then checks the air con, TV, refrigerator and other appliances to makes sure everything is working. As he leaves, you reach into your pocket to hand him a tip. How much should you give him?
At the beer bar, a beautiful hostess sits down next to you, striking up friendly conversation. After 15 minutes of practically melting in her arms, your friend urges you it's time to move on to the next bar. As you say goodbye to your new found love, you think a tip is in order. How much should you give her?
As the waitress in the restaurant hands you your change, you feel the urge to leave a tip. How much should you give?
After the blow job of a lifetime and an award winning fuck, you feel you have finally reached sexual heaven. On her way out, you know the girl deserves a tip. But you're not sure how much, so you ask and she says, "It's up to you." How much should you tip her?
Tipping in Thailand.
Practically anywhere you go, from the airport, to the hotel, to the restaurant to the bar, you will be confronted with the urge to leave a tip. How much of a tip should you leave? Should you even tip at all? What do the Thais tip? How do you know when and how much to tip?
We can divide tipping into two categories: that where tipping is a must and that where tipping is not always required.
As a rule, any girl you have sex with you must tip. Indeed, the tip a bar girl earns is essentially her salary. She is fucking for tip money. If you don't tip her, she will not only be disappointed, she may very well have the cops knocking on your door enquiring why you are being such an asshole and not giving the girl a tip which everyone in town would say she certainly deserves. At that point, you will certainly be wise to tip her whatever she may ask.
Most bar girls will be happy with a 1,000 baht tip for sex. Generally speaking, most bar girls will prefer "short time" sex, meaning after sex, they will get dressed and leave your hotel (rather than stay naked and spend the entire night). As they exit the hotel, you hand them the 1,000 note tip. Never pay a girl in advance, before sex. The rule is you pay after sex, not before. The exception would be in a massage parlor or brothel where you often pay the attendant in advance. In that case, there is no need to tip the girl any further.
Thais that offer other services other than sex, such as a waitress, a traditional massage parlor girl (i.e., one that gives a PG rated massage), a salesgirl, a bell boy, a receptionist, a maid, etc., do not require a tip. In other words, you are under no obligation to tip anyone at all, either the maid, a bar girl who flirts with you at a bar, a waitress, a hotel receptionist, etc. Why should you tip them anyway? If they clean your room, they are simply doing their job and the hotel is paying them. If they serve you food, again they are doing their job and the restaurant is paying them to do so. The same applies to any other service (expect sex). Anyone you run into and that offers a type of service is already being compensated for their work and you are therefore under no obligation to add to that.
Now, if you feel a tip is in order for a waitress, bellboy, bar girl or any other Thai who gave you excellent service, remember this when tipping. The average wage, for example, for a waitress at a restaurant is about $75-$100 per month or around 3,500 to 4,500 baht per month. Most waitresses at a restaurant make around 100-150 baht per day. What that means is you should not be tipping the same amount you would tip a waitress/waiter in the states. If you do, you will be handing them a ton of money, much more than they deserve. So how much do you tip a waitress (either at a bar or restaurant), a bell boy or any other Thai who offers similar services? As a general rule, 5-10 baht is a sufficient tip. 20 baht is overkill and if you tip 50-100, well, let's hope she sucked your dick along with serving your food. Those who hand a waitress a 100 baht note are handing her a day's wage. The equivalent would be like handing a waitress at McDonald's a $5 tip for a $3.50 hamburger he just ordered.
When should you not tip?
1. Never tip if the service was poor. For example, if the bell boy reached to carry the smallest bag, leaving you with the heavier bag, I wouldn't give him any tip. If the waitress took fifteen minutes to hand you a menu, I wouldn't give her a tip at all. If the travel agent said you have to go to the airport to change your flight, I certainly would not give them any tip. If the taxi driver who was supposed to pick you up at your hotel showed up late, I wouldn't tip him at all. In short, if you didn't get the excellent service you expected, don't feel any obligation to leave any tip at all.
2. Never tip a bar girl (in a bar) who asks for a tip. In the bar, every so often a bar girl will be bold enough to ask you for a tip. She will simply put out her hand and say something like, "Where's my tip?" Such a woman I would never tip (unless of course she came to my hotel and gave great head) simply for the reason that she is the type that thinks you should pay her for doing nothing. The rule in Thailand is this: you tip a bar girl after sex; before sex you never tip her. Therefore, any bar girl who asks for money, even a mere 20 baht to buy a snack, is hustling you and should not be tipped.

3. Never tip a taxi driver that works for a company and thru which you booked a ride. You already paid triple what the locals pay. Why make yourself look like an idiot and add to the inflated price?
4. Never tip a hooker who came to your room, then refused sex.
5. Never tip at a restaurant when there is a service charge already included in the price. You will know if there is by observing the bill and seeing the 10% add on. Many restaurants incur a 10% service charge into the bill, plus 7% tax. Such restaurants that do that are basically cheating you as there is no such tax/service charge in Thailand (if there was, all the restaurants would have them). Also, in any small restaurant that serves only Thai food (such as a restaurant that has no menu in English), no tip is required. Thais rarely tip in such restaurants and neither should you.
How much should you tip?
1. Sex. The going rate is 1,000 baht for short time sex. Add 500 baht if the girl spends the night. Pay her another 500 baht more if she swallowed and took it all the way up the ass.
2. Services. A 5-10 baht tip for general services, such as a bell boy, a waitress at a bar or restaurant, etc. is more than enough. If you wish, you can tip 10% at a high class restaurant, but check to make sure the tip is not already included in the bill.
3. Massage parlors. Those massage parlors that charge in advance only for the massage (and then you must tip the girl in private for sex), I would tip 1,000 baht for sex.
When you must tip.
You must always tip for sex. if you don't, expect a knock at the door from the local police.
When you don't have to tip:
Outside of sexual services, you are under no obligation to tip at all. Most of the time, Thais don't tip, so why should you?