Yes, you can change your NON-O retirement visa to a NON-O married visa in Thailand before it expires, provided you meet the necessary requirements after your first 12-month extension.
NON-O RETIREMENT VISA RESOURCES / SERVICES
Go to the Retirement Visa Section for information on requirements, including age restrictions, financial requirements, and necessary documentation.
For immediate assistance, contact Thai Visa Centre directly via LINE at @ThaiVisaCentre or Email them.
Explore recent discussions by using the Non-O Retirement Visa tag in the search box at the top of the page.
Most if not all embassies have stopped selling the one year multiple entry non-O visa. I would definitely check with the embassy to see if they are selling it, it's likely they just haven't updated their web page. You could also log into the E-visa application website and do a dummy application and see if it's an available choice
After you've taken your first 12 month extension based on retirement you, can when you apply for a new extension, change the reason to based on marriage by meeting the requirements
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