I have never been to Thailand but it is a well publicised statistic that Aids is prevalent out there and up to 30% of the the good time girls are affected. Please ...lets be careful out there.
I have nothing much to add to the previous posts except to say that if you are looking for some fun with a bar girl, make absolutely sure that it IS a girl before you get too involved.
My son lives in Bangkok and he has some scarey stories, lol