Is it necessary to show monthly transfers to a Thai bank account when renewing a one-year OA Retirement visa with a minimum balance of 800,000 THB?

No

Three options.

1. If your embassy will issue a income affidavit that shows you have monthly income exceeding 65k then you use that and need no funds in a Thai bank. US, UK and Australian embassies won’t issue those (perhaps others too).

2. Lump sum of at least 800,000 baht in a Thai bank in your name only. Must be in place 2 months prior to the application date (not visa or extension expiry). Must stay in the account for 3 months after the visa/extension expiry (not application date). Balance cannot go below 400k for rest of the year and must be back up to 800k two months before your next application date.

3. 12 x monthly international deposits of at least 65,000 baht. Once transferred in you can spend as much as you like. There is no minimum balance you must hold.

Some offices may allow a combination of 2&3 but not all will. You’d need to speak to yours to find out their particular rules.

I would like to know too!👍

If you have an OA and it's still valid, just do a border bounce and you'll be stamped in for another year. No bank account required

No it's either 800k or monthly deposits if you're below 800k for your extension