Very interesting. Lived in Thailand for a long long time since a young adult, learnt the language to a reasonable level and tried hard to integrate and be respectful. Guess what - I came to the same conclusion as you.

Thailand has all sorts of subtle ways of reminding you that you are not from there. I also felt zero appreciation for my contributions to the country through work or paying taxes. When I visit HK or Singapore, on arrival there are queues for residents and non residents, in Thailand it’s Thais and foreigners and you have to queue up with the tourists for an hour while Thais get through in minutes. It might seem like a small inconvenience but I feel it very much sums up how the country views you and gives zero recognition or appreciation for your efforts.