i want the vocab which means every seat in a theater is sold

Do you mean "Sold Out"? If tickets are still sold, then it would be "Standing Room Only" or "SRO". Are eithe of those what you are looking for, or is it some piece of theater slang?

Well if he's from Thailand, they might not understand what the phrase 'sold out' means since its more of an English culture term. Saying 'every seat is sold' may be better.

Justin, I don't think she would ask for a phrase that she used in the question.

We would say 'House full' or 'sold out' in Britain. All conventional theatres are all-seater here so 'standing room only' has no relevance to theatres .We do use that expression on buses when all the seats are taken.

Oh. Yeah. Woops. 'Vocab' makes sense now.