takemehome - you were neither the pilot, nor in receipt of the full facts & rules. Raising a valid concern is fine, but we can't be jumped-up if there is no reason to be so.
I spent whole flights in the flight deck as a fascinated pre-teen in the 80s until an adult pre-9/11 - if I were ever a distraction I would have been asked to leave. Fact is that it is not your decision to make, and the professionals in front will know if and when to make such a decision.
Is flight deck access restricted in Thai-registered aircraft? I don't know, but if the rules are the same as UK/US, clearly they are acting inappropriately.
I don't think it is appropriate for you to raise such suspicion and type someone's real name if you don't know the exact rules yourself.