[M.B.E.]

It's not really clear what you're asking when you want to know if you'll be able to play in Thailand.

(1) Are you asking whether the online sites will let you play? Yes, they sure will -- they don't care if it's illegal where you are.

(2) Are you asking whether the Thai authorities will have any objection to your playing online while in Thailand? I don't think you'll find anyone on this forum who knows the answer. Why not just ask the local police when you get to Thailand. It's a question of Thai law. But do keep in mind that being a U.S. citizen does not make you immune from Thai law (unless you are a diplomat or consular official). So if it turns out that it is illegal in Thailand to gamble over the Internet, you absolutely should not assume that the law does not apply to you because you're a U.S. citizen.