Not necessarily. I did mine whilst on the OA, bounced, got visa-exempt, then applied for non-O. The 65k transfers for the previous 18 months were accepted in lieu of the 800k. This is in Bangkok. I understand some other immigration offices are not so compliant!
You can't just "switch" from OA to O. You actually have to leave Thailand, come back in on visa exempt, and then apply for the O at an immigration office. I know for a fact Bangkok Immigration allows the use of 12 x 65k transfers, but each immigration office has their own rules