Sak Nak nearest and easiest to try, then if no go, carry on to Udon. I think Udon would be aware of the latest rules and are, I think, more user friendly.
Good luck!
1) Move to the Phillipines?
2) Set up a dummy address in the Phillipines?
3) If you have family or friends you could stay with, return to the UK for a 6 months holiday , say every 5 years to get your pension updated to the current rate?
4) And following 3) possibly keep a permanent UK address with said friend or family and get index linked pension paid into a UK bank account and transferred via Wise to Thailand? Would understaffed HMRC be any the wiser?