What are the options and requirements for Australian retirees applying for a long-stay visa in Thailand?

so if he does that...when it expires can he still use his visa

I agree with this. Starting with a non O single entry 90 day visa obtained outside Thailand with the reason for the visa being “intent to extend based on retirement” is a good option. It gives you enough time to get in the country, get a place to live, open a bank account and place the 800K THB in the account with plenty of time to extend it to a one year retirement visa

And as

@Stephen ******

says if you apply in your home country you can leave the bulk of your money in your home country and thus keep your money working for you in the way you currently have it invested ie in superannuation or offsetting interest in property investment or in high interest accounts with minimal risk and not needing to transfer it into a Thai Bank account

We did this one. Works quite well. Got the non O single entry while still living in Penang; opened a bank account and made sure that 800K THB was in there for 60 consecutive days and 45 days before the expiry, we applied to extend based on retirement. (You have to wait until 45 days or less is on the non O before applying to extend)

We the kept the cash in the bank as living expenses for the first year but you don’t have to once they stamp the extension. We do 90 day reporting which you have to do in person the first time then you can use mail or online if it works. And then 90 days before the expiry of the one year retirement extension we’ll put 800K THB more in the account. And like a shampoo, wash, rinse and repeat.

If you are already in Thailand then this option is not possible? You would need to go back to home country to apply for O-A long stay and return? Otherwise, if you have no plans on going back to home country, then there are no other options besides the O Multiple and Single entry which means having to cross the border every 90 days?

Me too!