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.