I don't know where you're getting that from, but the fact is Thais who were not born in the Chonburi province are still being turned away and told to either go to Bangkok or go to their home province for vaccination. I know what I'm talking about from firsthand knowledge. I am not aware of any changes to that policy.
No it isn't. There is plenty of vaccine now, mostly Sinovac. See today's Pattaya News for corroboration, 6 minutes in.
I don't know where the information you are posting as fact is coming from. Please cite your sources.
In my opinion nobody, foreign, Thai, or from Mars, should be turned away if they want to be vaccinated. If Thailand really wants everyone vaccinated, then vaccinate everyone - without making it so difficult for them.