You are in the same boat as me. You will need to leave the country before your expiration date and return to cancel the NON OA. You will get the visa exemption 45 days plus you can add an additional 30 days (1900 baht). Then you will need the 800,000 baht in the bank (for the 2 months before you apply). The only other option is paying an agent (approximatly 30,000 baht) to take care of it for you.
Here's my 2nd year stamp. Showed insurance and got year number 2. I am about to have to leave the country to cancel so I can start a new visa. But OA gets two years with insurance but no money transfer.