Avoid conflict. If you have a problem, walk away. Be willing to lose a little money if necessary. Avoid conflict at all costs. You absolutely will not win and might lose more than a little money.
This is a great tip.
The sad reality is this - the people there will smile at you and try to get your business, but deep down inside, they hate you. They hate the fact that you have a ton of money and can sleep with their women for dirt cheap. They know why you are there. I'm not trying to make you feel bad and, as I've said, I've been there too so I'm no better than you, but you need to be aware of this dynamic.
Because of this, you need to know that if you get into an argument or fight with a Thai, you won't be fighting that one Thai. You'll be fighting 10. And they'll fight dirty. They don't care what you are fighting about or whether you are right....if it's a foreigner vs. a Thai, they will jump in and help the Thai. Numerous stories of this. And who do you think the police will side with?
As BobLaublaw11 says, smile and walk away. Let them win. Swallow your pride. It is by far the best way to handle these situations.
Generally speaking though, if you are nice and courteous and treat people with respect, you don't have to worry about this. People respond to warmth and cheeriness with the same, no matter where you are. Laugh and joke with them. You should have a blast. It's those douchebags who come from foreign countries and look down on the people there that end up in the hospital or worse.