Originally Posted by CkCrunch

I just did this trip 3 days ago - HKG-BKK on TG and BKK-USM on PG (separate ticket). No problems at all.

They can interline (I used airport express checkin at HKG), but I was not able to get a boarding pass for the PG portion - this was because I bought my PG ticket on their website with a credit card and PG wants to verify your your credit card if you purchased it on their website. This could be a problem if your connection is tight at BKK - the PG transit desk at BKK sometimes has very long lines. But they have so many flights to USM, they will board you on the next one if you miss it (I saw them do this with the couple in front of me).

If your PG flight is on a separate ticket, you will need to show them your ticket number. I didn't have it, but after 15 minutes on the phone with PG, the TG agent was able to find it for me.