I would say that climate, food, people, and affordability are the main factors.

It has become way more affordable over the past few years due to the price of the Bhat rising against the dollar. Nevertheless, it is still way cheaper than many other places, and if you can make around USD 1,000 per month online (which is relatively easy to do), you will have a pretty decent life.

It is an exciting mixture of Western and Eastern culture while still being uniquely Southeast Asian and Thai! It's a great place, and there are many things to do.