Rob or Tod may offer different advice here and that maybe more knowledgeable than mine. But the way I experienced this, you cancel WP then have a very limited amount of time to cancel the extension. Where upon you will then be given 7 days to exit.
So, what you are technically saying is that every tourist now entering Thailand on a 30-day exemption has to show evidence of 20k THB on arrival. How do they determine who is liable to show this evidence?
I now live in Vietnam and visit once or twice a year, as do many foreigner teachers here who have to leave the country to come back to Vn for visa purposes. Are they also required to show this if arriving on a 30-day tourist visa-exempt basis, or even just for a short break holiday, as I plan to do in January/February?? It now seems that even visiting or living in Thailand is becoming a real gamble/ shitshow.
If your ex missus is letting you live there without a fuss, surely there must be some way she can be approached, as a woman who let's you do this doesnt sound like the unapproachable or vindictive type.
Sorry to be blunt but from experience, it sounds like your company could not give a shit, because they could easily sort out the WP for you. Time to move on I would say. I presume you are still working for them. So just say good bye. You will need to cancel your extension of stay of course. Or just go work in a different country, like Vietnam for example. More money and lower cost of living too.
So, what exactly is the purpose of the extension? You have to have the non O/B visa to get work permit then get the extension after the work permit. Why can't one stay on the Original Non O/B visa after getting a work permit? Something that has always confused me.
Guaranteed they haven't started anything yet, as one, you would need the paper work from the school to apply for a non B visa which they would require your passport to do. Then they can apply for your wp. Regarding working during your wp application, thats pretty much the way it roles here.