The airline most likely would require onward flight within 60 days.
One option is "rent a ticket"
Search "onwardticket.com"
Process for visa exempt to Non O marriage outlined here.,
https://aseannow.com/topic/1315828-visa-exempt-to-90-day-non-o-spouse-visa-conversion-in-thailand/
Do you have a Thai bank account in your name only?