Can I extend my Thailand retirement O visa and get another 90 days by leaving the country?

@Ronnie ******

in case you got a "single entry 90-days Non-Imm-O retirement visa", you can only change from the visa to the "one year extension of stay" by showing funds of 800.000.- THB in a Thai bank account. If you don't switch from the visa to the "extension" your time will be up within 90 days. As this visa was a "single entry", you can neither extend or repeat it. You need to exit Thailand before the 90 days stay permit is over

Where did you get your visa?

If you got your visa inside Thailand from immigration you have a 0-entry visa, meaning you were already in Thailand when you got it. Purchasing a multi-re-entry permit on this would be a huge waste of money as the re-entry permit is only valid as long as the visa, so for 90 days.

If you got your visa before you went to Thailand, do you have a SINGLE entry non-O visa, or a MULTIPLE entry non-O visa that was issued from the embassy?

If you got a single entry non-O visa and then purchased a multi-re-entry permit, you once again wasted a lot of money as this visa and re-entry permit is only valid for 90 days.

If you got the multiple entry non-O visa from the embassy, then you will be stamped into Thailand for 90 days every time you enter the country until the visa end date written on the visa itself.

A re-entry permit purchased from immigration is never going to give you more time by leaving the country. All a re-entry permit does is mean your stamp is not immediately invalid when you leave Thailand, and when you return you are on the same stamp with the same end date.