What are the requirements and recent experiences for converting a tourist visa to a Non-O retirement visa in Thailand?

I did it twice in country after different work assignments, albeit many years ago. Jomtien immigration told me to make sure money had been seasoned for 2 months before applying for the non-0. As I said, it was many years ago, so things may have changed.

You may have a problem with your Thai bank as you can’t have an account in a tourist visa you’ll need the 800k here why don’t you apply at home the funds can be in any bank

It depends on which office you go to but in Ubon going from tourist to retirement requires a letter from your embassy verifying your income and if you’re from the US, that embassy quit doing that 4-5 years ago.

The solution is go to Lao, (Savanakhet for example) and get a 90 day non-o retirement. They only require bank statements and proof of income for the 65K method, I’m not sure how long you would need 800k in the bank if you went that way.

After the 90 day you can can do a renewal and extend for a year. No embassy letter required for that.

I believe Jomtien is the only office that requires the funds to be seasoned for a conversion from tourist to non-O visa.

You would need to check with Pathum Thani immigration to see if they support conversions from tourist to non-O visa. Not every immigration office supports this.

The other issue you may run into is that you need at least 14-21 days left on your stamp at the time you apply for the extension, so depending on when you enter Thailand and when you'll have your money in place, you might not have enough time. You should definitely apply for a tourist visa to maximize and get up to 90-days to get everything done, if that immigration office allows conversions.

You do need to make sure that the transfer of your funds shows as an international transfer as that's a requirement for in country conversions.