Could it be that you are mistaking the need to leave the country with a 90-day report of your residence ? Non-O does not require you to do a border bounce
Sorry to hear about your wife. I would try to get a usufruct written in the chanot of her land. Maybe she needs to give power of attorney (if possible) to a relative to arrange this at the land department. Get sound legal advise !
I have used 4 Immigration offices, all required a TM30 within 24 hours after entry.
And as a TM30 is basically a residence report, you still have to do it, even if you don't call it a 90 day report. BTW, aren't TM30 and 90day report done on the same immigration website form?
I think you have to report your place of stay within 24h after entering Thailand nonetheless. Either by yourself or by your hotel/landlord. This is what then will reset the 90 day count. In my understanding.