Sorry, I just went back and reread the OP and noticed it said "My flight transfer from HKT in BKK was the worst I have ever experienced anywhere in the world" I incorrectly assumed it was the flight from HKT to BKK that was the worst, so my apologies for confusing that issue.

So actually it now has me even more confused as to why someone would call a domestic-to-international transfer at BKK the worst unless one hasn't had much international experience. My personal opinion of the BKK transfer process is that it's up near the top for ease in transferring. Of course you must consider the size of an airport. You can't compare a dinky airport that only has a few flights a day, or even a medium sized airport with a very high-volume airport like BKK. I can't think of any large airport in the U.S. or Europe that I'd rather transfer in.