@Amber ******
a work permit doesn't let you stay IN thailand it lets you work here, so I would imagine you have either a 90 day Non-B VISA or an extension of stay based on employment.
Now whether you can cancel that extension based on employment, get a covid extension THEN have your school give you documentation to apply for an in country Non-ED visa is between you, your current employer, the school you're enrolling in and the immigration office you'll be using.
Your topic is SO much different from this one, if you have more questions please make your own post