This is low season, so 2 hours seems like a massive 'abundance of caution' ! But I am in NZ at present so can't provide an actual data-point.

I do have a BKK-HKT-BKK mini-mileage run in late July to regain TG Gold, and I'd hoped to remain airside. It has been a while since I have done this at HKT, and I can't actually recall if I can remain airside or if I need to flow out into the public area, and then back in through security.