Hello I'm a new user here!

Me and my parents are going to Thailand at the end of March.
But the problem is that my flight is arriving at 6 AM and theirs at 3:30 PM..
So, do I have to pass Immigration control to wait for them, or can I wait for them and then pass Immigration control with them?

What are some things to do at Suvarnabhumi Airport if I pass/don't pass immigration?

Thank you!