okay lets recap your options
@Kristin ******
because you seem to not understand your limited choices.
You can stay in thailand on the 90 day entry stamp you got off that Non-B until it runs out. It doesn't matter if you work for the company that gave the documents or not to you so you could get the visa you can stay the full 90 days you were stamped in for
BUT
You cannot get ANY extension on it (period, end of story).
You need to either GO to a border, stamp out of the country, stamp in & out of another country and then back into thailand to get a 30 day visa exempt entry (no need to fly out and back)
OR
you need to go to a thai consulate in a nearby country and BUY a single entry tourist visa (that gets you stamped in for 60 days). Those are your choices.
As I said you CAN stay until this 90 day stamp from the Non-B runs out before you have to leave,
Good Luck