Whenever you travel to a foreign country, it's always a concern about how to tip or whether you should tip.
Unfortunately, Thailand is becoming more and more used to tipping with many restaurants, hotels etc adding a 10% service charge to the bill. The issue with this is that you can't be sure that what you tip actually gets to the staff. Basically, this is Thailand and it would be a very special establishment that actually does the honourable thing and gives tips that have been added to the bill, to its staff.