In short, your country isn’t supported right now and there’s nothing you can do about it. Just wait and see if they add your country again. Brave is working to add countries back by the end of the year. I’m not sure about Thailand, so all I can say is to be patient and check back on occasion.
You can still earn BAT but you can’t connect Brave to Uphold or Gemini. This is because Brave has halted those connections. You can still use Uphold but not with Brave. (Brave’s decision) They did this because they needed to update their systems, adjust to government regulations, deak with a lot of fraud and try to improve on fraud detection & prevention, etc.