Thanks for the informative thread Atlantis.
There is also some information on the Nok Air website, even though it says up to date as of 15th November 2021, I don't think it is as I think UTH accept RT-PCR test results (but no, not just vaccine (according to info at DMK):
https://content.nokair.com/en/Special-Page/TravelCOVID.aspx
There is also similar information boards on at Don Muang, although in Thai. Use Google Translate camera on the ones at ground level. This morning, it showed all provinces accept at least either vaccine or RT-PCR
Most of the provinces require EITHER vaccination OR a RT-PCR test OR an ATK test - any one of those three. It is misinformation to say only vaccince is accepted.
As an unvaccinated person, today I have come out of 10 days ASQ, taxi straight to DMK, flew Thai Air Asia to Sakon Nakon using the RT-PCR test done three days ago in ASQ. It was perfectly acceptable. At SNO, I got my bag and walked out, no need to see a health official or anyone else. They did want some QR code scanning at DMK that went to LINE but it wouldn't work on my LINE. No one asked for it at SNO
Domestic air travel is open to the unvaccinated as of 8th November 2021, it is misinformation to say otherwise. Of course, things can change and other provinces may yield other experiences.