Hotels cant all be closed. There has to be at least those for foreign aircrews. Whether they will permit an overnight before travel for passengers is the question?
It is 8 hours max transit time I think. The connections are set up so it is only a few hours coming from West Coast morning departures you get to BKK at 23:20 There might not be an evening flight to BKK every day KAL cut their schedule.. I just did it from LAX. About 2.5 hours ground time.
And the instructions in the test packet. Normally thrown away. 2 negatives test from different sources last week. Both useless for boarding flight to Thailand.