Can you switch from an O-A visa to an O visa while in Thailand?

What is the reason to change from OA to O?

You couldn't "swap" to anything from an OA,

If you get the OA visa from the thai consulate in your country before you come here, you get stamped in for a year (or as long as your mandatory insurance is valid for up to a year)

THEN

when that year runs down IF you got another year of insurance you could exit/re-enter before the visa itself expired and get a whole new year entry stamp (or as long as the insurance is valid for up to a year)

Most people on OA visas (who plan it out right) manage to get almost 2 years of stay out of that one year visa by renewing their insurance and bouncing out/back for the second year entry stamp.

However IF you're wanting to get OFF the OA visa you'd have to exit the country, get stamped out, then either buy a new 90 day Non-O visa from a thai consulate before you come back OR enter free stamp 60 day visa exempt, have the 800K banked in a thai bank account in your name only and apply for the in country 90 day Non-O visa at the immigration office where you live.

There is no way to "swap" an OA for an O without getting completely off the OA and starting the Non-O visa/extension process from scratch