Visa or permission to stay? I have a non-O from Savannakhet based on marriage. Last year my visa expired in May but I remained in the country until September when I renewed. So long as you have leave to remain the visa expiration does not matter.
I did it in Nakhon Ratchasima a few years ago. I remember going to immigration and asking how to do it. At the time the money had not been in the bank for long enough so I extended my permission to stay for 1900 THB and returned a month later when the financial requirements were satisfied. No problem.