I made the TG676 to UA838 connection in the first week of January. The TG flight arrived 20 min late. The flight attendants allowed connecting passengers to exit first and the security check took 5 mins. The security check area was well staffed to rush passengers through. Make sure to get your UA boarding pass from the Thai checkin counter in Bangkok (I could not do this with the Thai or UA apps). My checked suitcase made it too!
Good luck!