Thanks for your reply Joe,
I've got the 400k in bank, only moved last week, we attempted to apply for a marriage extension yesterday but were denied because it's not been in my account long enough (we were advised that we might be able to get away with it if I also showed my job offer/contract showing my pending income over 40k, but no luck).
My dilema is that I have a great job offer that is willing to wait until the start of september for me, but not much longer, so I'm really trying to get my visa sorted before then. I should be able to start it remotely while locked up in hotel quarantine.
Some more planning shows that a flight to dubai and back again will be an option. Dubai only require a 72h valid PCR test for entry, no visa. I'll just lurk in the airport for 12h and return back to thailand. I have a friend in the hotel so total costs will be probably about 60-70k thb.
The alternative seems to just be wait out the 2 months money period, during which I'll have to do another COVID extension to my visa, then apply for the marriage 1y year visa with my wife. I'll lose my job offer doing this though, which was hard fought and a rare chance for someone of my skills.
Very frustrating that the land borders are closed or all this could be avoided quite easily. Very upset at the moment.