A reader of the French forum is asking :

Is it possible to modify a visa O marriage to visa O A retirement at an immigration office inside Thailand?

I guess this question had been asked 586974 times... sorry

O-A visa can only be obtained in your home country.

He can get an 1 year extension of stay based on marriage or retirement at his local immigration office.

Normal confusion caused by people calling an extension of stay based upon retirement a OA visa.

He can apply for a extension of stay based upon retirement during the last 30 days of the 90 day entry from the non-o visa. 

Or perhaps he has a extension of stay based upon marriage and wants to change the reason for it to retirement. That can be done shortly before his current extension ends.

If they currently have an extension of stay based on marriage (often wrongly called a married visa), and they want to change the reason for the extension to retirement (often wrongly called a retirement (O-A) visa), they can. But, usually, only at the end of the current permit to stay.

 

If they are asking about an actual 'O-A' visa they need to apply in a country they have legal residence in.