How can I open a bank account in Thailand while applying for a Non-O visa?

E-visa will have it. I was told I could not get non immigrant O inside the kingdom, btw.

well it is like Brandon said: the Non-Imm-O retirement visa is not listed on the WEBSITE of the Royal Thai Embassy Singapore, however it will show being applicable once you start the E-Visa Online application

To apply for nonO in thailand....u must already have a thai bank acct....

I had absolutely no problem finding the non-O visa for the Thai embassy in Singapore on the e-visa site.

The e-visa system is standardized for all embassies. The non-O visa is available from EVERY Thai embassy and consulate.

And if for some reason you didn't want to apply in Singapore, you would still not be able to get a bank account in Thailand so that means Thailand isn't an option. So you would need to travel to a different country and apply through the Thai embassy in that country.