I don't check bags that often but don't usually see the delays you're talking about. Perhaps it's due to my flights typically being on a 734 (on TG), whereas you're likely on planes carrying significantly more pax. BKK also is quite good at adhering to the principle of 'priority baggage'. That is something the other domestic airports have left me desiring.

Two days ago I flew in on PG (short int flight) and we parked at D8. I'm not used to getting a gate on this segment, whether on TG or PG. Anyway, I chose the wrong immigration line, the guy was utterly incompetent. The lines around me were processing 5 in the time it took him for 2. After 25 min on line I got to the carousel and there were no pax left, maybe 7 bags still going around.