25.000.000฿ my guess for pocket money and may run out if you get health issues or live long.. 50.000฿ per month is good starting point for pocket money and then you think your housing and healthcare top of that. How long...
Depending on your purpose of visiting Thailand. Immigration officer can be able to extend your stay for a period of up to 1 year and extend your stay annually.
Bangkok bank health insurance was 7.900 baht January. No needed but better than pay agent because you still get that insurance quite cheap if agent fee is +3.000 bahts🙏
Deposit requirements differences little and some times you need to keep balance over x.xxx baht.
You can do border run and come back in exemption and apply non o retirement visa. It's good move look few days Laos and come back. Take cash because my friend were asked some lubrication maybe 1000baht when he did same day border run without agent. There's no problems if you can show money when you come back. I did border run between non o to non b and I just went desk to desk and back home and pile of cash save that trip. I didn't pay any tee money but they were interested about financial side and money was pouring out everywhere and the customs officers had a smile on their faces🙏🇹🇭