@Nick ******
Always best to apply for a regular 90 days Non O at home before you leave. Then you can open a bank account and apply for one year extension of stay within two months.
If you come on the Non O-A, you’ll maintain the mandatory thai health insurance requirement for all future.
The requirements for to apply for the Non O at home or in Thailand are the same. But at home you can apply just with income min equal to 65K baht or funds equal to 800K baht. In Thailand you’ll need to bank 800K baht in a Thai bank account for to apply.