If you happen to be in Thailand after the last “enter by” date shown on your Non Imm O-A visa you can leave without a reentry permit and re-enter visa exempt (provided your from a country that is approved for visa exempt entry) and apply for the Non O. You don’t have to wait until the end of your permission to stay date. Just check to be sure you are past the last “enter by” date shown on your O-A. You can apply for the Non O from within Thailand.
TM30 is probably what you’re referring to. Each district has its own rules about updating the tm30 after arriving back in the country. Others will be along shore with updates…I’m sure!
understand that each monthly deposit of 65,000 must be shown to have come from overseas. Check the code beside your deposit amount in the bankbook to be sure it appears as an international transfer.
If you do go the route of applying for a Non-O visa while inside Thailand, you won’t be required to show health insurance. You will, as others have said, need funds in the bank. 800k if you go the non-O retirement route or 400k if you go the non-O based on marriage to a Thai. You will also need to have actual marriage documents for the latter. There’s no non-O visa based on having a fiancé.