@Steven ********
I deleted it, you do not know if the OP can get a Visa Exempt Entry. He is on an Extension of Stay based on working, which has to be cancelled at Immigration before making a border run.
Your Idea:
Visit Immigration and cancel your stay
Go on a border run (if possible with the passport)
Conversion to new Non Immigrant O visa, cost 2.000 Thb
After 60 days, apply for Extension of Stay.
My idea: cancel current Extension of Stay and apply for new one, save a lot of money, visits to immigration and possible border run or fly out or even go back to home country first.