Immediately open bank account and send 800k from abroad.
After 80 days Goto immigration and ask what exactly they want to see. (Bank statement and certificate, a passport foto, book bank with a transaction of the same day, ID of Thai wife, your passport,…).
Get those things and return with 1900 baht.
If you plan to exit more than 3 times per year, get a multi reentry permit.
I just did my EOS yesterday as I’ve been doing it for over 10 years now. Costs 1900 baht and 5-20 minutes waiting (and time doesn’t count anyway for a retiree ;) )
Why is your current insurance not usable for that?
I had to get a new one because Swiss insurances can’t be used once I deregistered in Switzerland. So I got an expensive one with coverage even for a heart transplant (better safe than sorry).