A medical visa won't work for you. You can potentially get the DTV visa based on medical treatment if you regularly have to attend hospital and that hospital will write up a treatment plan signed off by one of the recognised doctors there. The Non-O based on being over 50 is easy to get and renew, less hassle than the Non-O based on marriage
OK, but with your history I'd suggest you contact one of the "fast track" companies that can ease the entry back into Thailand or you run have a high chance of being refused entry. Why not apply for a proper visa while in Dubai? Maybe a DTV if not old enough for a retirement visa?
suggest you speak to the visa run company you already engaged with and see what they say. Who knows how long Cambodian borders will remain closed but it seems to be escalating to me
Laos and Malaysia are your options by yourself. The visa run company will take you wherever they can get you out and back in. With your history you'd be foolish to try it yourself