Its not a problem as long as you can show 12x monthly transfers of over 65k. Irrelevant of what bank account, as long as it’s a Thai bank account in your name only.
Once you’ve been approved for the 65k per month method then there is no requirement to keep any funds in your account. As soon as the transfer hits your account you can spend it at will.
The requirement to keep the funds in the account was based on the 800k in the account method. A completely different scheme.
That’s fine. Some people set up a standing order to transfer X amount of whatever currency to send to their Thai account to equal close to 65k. Except sometimes it doesn’t quite cover it and even if it’s just a couple of baht short it won’t work for using the 65k method.
You need 12x monthly deposits of 65k or more to switch methods. You can’t go below 400k from your previous extension as that was a requirement for that extension.
Probably a good idea to put the account back up to 800k two months prior to applying to use the 65k method just in case there is any sort of glitch. If there was then you’d be back to square one without an option to renew.