it is I travel monthly into Thailand never been asked. Asian airlines and most continental european airlines don’t ask. US based airlines from what I have heard ask all the time.
I live outside of Chiang Mai in Mae Wang but we have a second house in a Karin village at 1200 m. I can managed without air conditioning but not ideal. You need to get to about 1500 meters minimum. And most of the land at those altitudes are parks or occupied by hill tribes