TR visa supposedly still eligible for a single 60 day Covid extension. But only after 30 day extension first (at cost of 1900bht). As to whether it is granted or not - unsure. Reports of some ppl being denied a 60 day Covid extension, and getting the dreaded 7 day stamp
I'm pretty sure the second pcr test also requires a hotel booked (and isolation until negative result received). Probably too many people skipping the second test on the original test n go setup :)
also need to consider what (if any) effect a transit stopover in another country may have on entry requirements for final destination (ie length of time or where).