Can I switch from a Non-OA extension to a Non-O visa by exiting and re-entering Thailand on a 30-day visa exemption?

You can indeed exit/re-enter the country (either by air or land), to get OFF the OA extension you currently have, come in on a 30 day visa exempt entry.

Then you'd get your documents together, go to your immigration office and apply for the in country 90 day Non-O visa and after that the year extension.

People do that process a lot to get off the punitive mandatory insurance that OA visa/extensions entail.

You don't mention where you are in the country, but at most offices you can apply for the in country Non-O visa when you have sufficient time on either a 30 day visa exempt or a 60 day tourist visa entry stamp (usually between 15 and 21 days depending on the office)