An air quality index average below 50;
... year round, NOT in TH
Access to clean sea water and beaches (like the Andaman vs. the Gulf);
... Andaman is not clean either, in any developed area
Access to restaurants, good hospitals, and markets?
... restaurants & markets, no prob ... good hospital, need to be in a small metro area, which mean polluted sea water. 2 out of 3 is the best you'll get, maybe.
All 3 of those criteria in one place isn't found in TH.
IMO