I have been in Thailand just over 15 years.
I arrived Thailand from NZ on a OA Retirement Visa..
July last year 2024 I decide to change to a Non O Visa.
Late in August I went to Cambodia at Chong Chom without a re entry permit.
Came back into Thailand with 60 days.
Went to immigration and started the process.
I later extended for another 30 days.
At the end of November immigration stamp the Non O into my passport.
Surin Immigration at Surin and Kap Cheong were fantastic.
I cannot praise them enough.
800,000 baht is required in the bank.
I was able to do it with a letter from the NZ Embassy.
Not all all Embassies do that now.