Can I use two bank accounts to meet the proof of funds requirement for a retirement visa extension in Thailand?

FWIW, when applying for an e-Visa, I used two bank accounts, and I received the Visa. That could have no bearing at all on how a different embassy or official would handle your situation. Now, I keep one account just for submission for visas.

There is a corollary to Murphy's Law: If it goes right, Murphy is setting you up with a false sense of security.

I would use 1 bank account to keep the 800k and the incoming monthly 65k in .., then use another bank account to transfer the 65k in (once it clears) and use that separate account for all your spending needs.

Then after your first year extension, put the 800k in an investment account but keep the original account open to continue receiving the monthly 65k so you can show immigration your 12 month statement each year.

By keeping the 800k & 65k deposit in its own account it’s much easier for immigration to see/track for immigration purposes.

And using your 2nd separate account for all your living expenses keeps everything nicely separated.

I have 2 accounts. One immigration account. Dead funds for visa. Unless dying leave the 800k alone. Another account banking app spending scan etc. no immigration hassles

We have 3 accounts. My visa account, my wife’s visa account, and our daily expense account. CNX doesn’t have an issue as they clearly see each of us have the 800k.

But CNX is a pretty laidback IO.

While there is nothing in the rules stating you must use one bank account I think you're making the process a lot harder than it has to be trying to 'push that rope' (have 2 accounts) with your immigration office :/

Certainly go talk to them well before you need to get this next extension and see what they say, with so much latitude given individual offices there's no telling what they will allow

I tried to do more than one bank account and it was rejected by immigration

Can you use two accounts to meet the proof of funds for retirement extension? Yes,

However you're doubling the paperwork you need from the banks, year detail transaction report, bank letter, updated bank book the day you apply on both accounts

AND

you'll have to make sure that the balance never went below 800K on the combined account balances during the 3 months post extension seasoning and then that it never went below 400K the rest of the year.

Note; some immigration offices take a dim view of people using multiple accounts, so definitely check with your office to see how they will react to it..