Don't worry about all TG connections within BKK. TG almost always takes care of you. If you're incoming flight is late they'll usually hold up your connecting flight for you and see that someone meets you at the door of the plane to rush you to your connecting flight. Unless your incoming flight is unusually late you should be fine. I've done a connecting flight of only 50 minutes and had 30 minutes or more to spare at the TG lounge while I waiting for my flight to board. This is assuming your luggage is checked through. If it's not, then you could easily have a problem, but no reason for it not to be if you're flying all on TG.