Can I meet the monthly income requirement for the O retirement visa extension directly, and what documentation is needed for income verification from rental properties?

The monthly income amount for "Retirement" is 65,000 each month - not 67,000 Baht each month.

Hello

As an aside. I know a person who worked in Cambodia for many years and still has a bank account there. He transfers in from that account 65K baht every month, then withdraws it as cash, goes and transfers it BACK to his cambodian bank account, and then transfers it back in to thailand next month. He's done that 2 years now and gotten his yearly extension without question each time just bouncing the money back and forth. The main account that shows the incoming transfers only show the money withdrawn as cash not any out going transfers.

Immigration will only accept monthly deposits into your personal Thai bank account. They do not care about rents you receive overseas. If the rents are from property in Thailand, then they might accept it if you are a registered Thai company, but that doesn't sound like the case. It sounds like you have your cash coming in from rents in your home country, and only want to withdraw what you need monthly from an ATM machine, and not bring the monthly requirement into a Thai bank account. Immigration will not accept any notarized letter from anyone designed to verify your income. All a notarized letter/document signifies is that you signed it. Not that it is truthful. That is why immigration quit accepting notarized letters from embassies, as they would not certify that the document was the truth. Notaries do not do that. All they do is verify that the signature is actually the same person that signed the document, and that is all it verifies.

67,000/month is 804,000 over a year. Why not save yourself a lot of trouble and just go with 800,000 in an account up front?

IF you come from a country where the consulate here doesn't issue an affidavit of income from abroad notary (like the US, UK and Australia who all stopped issuing them at the end of 2018) and you still want to use monthly income method your only choice is to transfer 65K baht a month into a thai bank account in your name only each month, every month for the previous 12 months before you apply for your yearly extension.

I have never seen someone get a year extension by only showing a few months of incoming transfers, even if it's their first yearly extension. To my knowledge you need 12 months of transfers <- which is why everyone I know that gets their first year extension uses banked money method

Immigration doesn't want proof of your income. They only want to see the deposits have been made into a Thai bank account. Most immigration offices want to see 12 months of deposits prior to the extension. Some may let you get away with just two or three months for the first extension. You would need to get a letter from the Thai bank certifying bank statements showing the deposits. If you don't have a few months of deposits at the time you need to get your extension it's not even worth trying.