@Zane *************
run away, now!
1. You're working illegally in Thailand. If you're caught (slim chance these days), you'll be deported.
2. It's somewhat easy to convert an extension of stay based on COVID-19 to a Non-B visa and an extension of stay based on employment. (probably) no excuse.
3. I worked for a teaching agency. From the agents viewpoint, you're replaceable. Your agent is trying to get money out of you that he should be doing. Pay the following fees:
Non-B visa:2K THB
Extension of stay based on employment: 1,900 THB
Work permit: 3K THB (if my memory serves me right).
If you give the agent the money, expect more excuses. That's what happened to me.