Tipping in Bangkok is not obligatory, but is fairly standard practice, particularly when the service meets your expectations. Many restaurants today include a service fee on the bill, so please check to see whether this has been included or not and if so, it is not necessary for any additional tip. If not, then an additional tip between 10% and 15% would be normal; remember that wages in the service sector are not very high, and some recognition for good service will go a long way to ensuring that the high levels of service that one has come to expect in Thailand can continue.