@David *****
I don't think it's cost effective to get the re-entry permit.
1. During the 15 days in quarantine, you can't leave quarantine to get the extension of stay. 2. A re-entry permit is 1K THB. A new visa is about 2K THB (or thereabouts, in local currency).
My advice: Leave, apply for the single entry Non-O visa when you apply for your Certificate of Entry, and then return on the visa, it'll make life much easier for you.