How soon can I withdraw 400,000 THB after renewing my retirement visa in Thailand?

I understood the rules changed whereby one had to keep THB0 6 months before a visa application and 6 months after. I'd appreciate any information on this.

Are you starting to do the 12 65k montly international transfers for your extension next year? That is how you free-up the 400k for withdrawal (and the 65k can be withdrawn immediately after deposit).

The rule is you must have the 800,000 in the bank for 2 full months before you apply for your extension (not before your extension ends, but when you apply) and then it must stay at 800,000 for 3 full months after you receive your extension. Then it can never drop below 400,000 the rest of the year. You bring it back up to 800,000 next year 2 full months before you apply and repeat the cycle.

As part of your application next year they'll want to see a 12 month bank statement to see that you kept it at 800,000 for 3 months after last year's extension and then never let it drop below 400,000.

800k 2 months prior to application and 3 months after. Then can drop to no less than 400k and has to back up to 800 2 months prior to next application.