To ask in Thai whether somebody is a Thai, can I just ask "ben kun Thai" or is it rude to not use any pronoun?

Answer 1

If you are asking "Ben kun Thai", people may not understand this. "Ben kun Thai" means (I am) a Thai person, it is not a question.

If you want to ask whether somebody is a Thai person, you would say "Pben kon Thai rue pao krub" (if you are a male) and say "Pben kon Thai rue pao ka" (if you are a female)