Almost certainly impossible for you to find a job here. Most unskilled jobs would be reserved for Thai nationals. If you can teach English then you may have a chance.
If he leaves without a re-entry permit then his visa (actually the “allowed to stay stamp” as the visa is used already) would be finished.
Depending on when he’s wanting to return he could get a re-entry permit to keep his allowed to stay date “alive” or he can apply for a new Non O visa for the next visit.
You could come in as visa exempt and convert to a Non O based on being over 50 if you have 800k in a Thai bank account. If you don’t have those funds then an agent will be able to help you.
Ok this post is getting weirder. Why would a Thai citizen that owns land have to divorce a foreigner to keep land?
I’ve not seen a single reference anywhere that London is requiring travel insurance to issue a Non O visa. Why would they? It’s not a requirement to issue one, nor a requirement to get an extension off one.
IF that was a new requirement then I’m sure this forum and others would blow up with posts about it. I suspect it was a “lost in translation” thing.
Your local immigration office should be able to give you a conversion to a Non O (not all do) and from then onwards a yearly extension as long as you meet the financial requirements.
If you can’t then an agent will be able to help for a fee.