There was a thread about this a while ago, also a trip report about flying with the Thai Royal Family. Unfortunately, I don't have time to search for those threads now.

My only near-celebrity encounter was last year when the check-in agent at the RCC told me I'd be sitting in F with Carlos Santana and his entourage (an invasion of privacy for Mr Santana for her to tell me that, though). Unfortunately, that flight was canceled before boarding, and Mr Santana was rebooked on one flight, and I on another.