We will both have our onward boarding passes, as my companion will get all the boarding passes issued in HKG and bags checked all the way through.

For myself, I'm not really sure as my CX/TG tickets are separate and not sure if CX in HK will check my bags thru and give my both boarding passes. I may need to collect my bags in BKK and re-check in. In any case, I should be able to manage this quite easily in order to be back inside the airside area before the 2230 arrival of the TG flight from HKG.

From what you're saying, I can't go to the arrival gate and I need to wait somewhere on the departures area that's near where the arrival gate drops pax. Is that correct?