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.
Yes. Just go in and ask to update. All you need is your passport and your old tm30 slip. Only done at the main office near the airport…behind the drive up 90 day report window. Not done at Central Festival. Takes five minutes
Why not enter visa exempt and then apply in Thailand for a Non-O visa and then the annual extension thereof? Do you have funds available to deposit in Thailand?