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posted by The Bangkok Consultant
Recommended: Using your mobile in Thailand
Ah, this is a common confusion in Thailand. Usually when you get a bill, or you're quoted a price, sometimes you'll get a ++ at the end of the price e.g. 1000b++.
This indicates that the service charge and tax will also be added to the bill. This is normal for posh establishments, but not so much when eating street food or at small restaurants.
Currently the tax to be added is 7%, and the service charge is at the discretion of the hotel or bar, which is usually around 10%.
If you get a bill with just one plus that usually means there's just tax to be added.