@Baz *****
I did accidentally bring an air rifle into Thailand in a container too, I didn’t know at the time it was illegal. I just kept it in the house and used it in the yard from time to time. Never had any issues. If you do bring it I wouldn’t recommend telling a lot of people about it. Also, I think it might be legal even if you can find plastic pellets for it as from my understanding the difference between a gun which requires a license and one which doesn’t is whether or not the projectiles are metal. High power BB guns with plastic, gel, or glass ammunition are legal.