3 months after receiving the non-o retirement visa extension I can transfer 400k, or 800k, or even everything to the new account.
After that I go to the BBL Pattaya and have the bank book updated to prove that I had 800k in it for 3 months.
For the second retirement extension I go to the BBL KK on the day I go to the immigration office and have the bank book updated and ask for a bank letter.
Then I go to the KK immigration office and show both bank books and the bank letter from the BBL KK to prove that I have 800k in my Thai accounts.
For the third visa extension I no longer need the old BBL account.