Didn't intend to work here but been offered a job with paperwork for work permit. However; is it possible to obtain work permit with a Non O?

Normally such an entry visa can be used if for family member being Thai but recent reports have varied from place to place. You should always be able to extend for family reasons however and maintain work permit.

Thanks Lopburi. So it is possible to get a work permit on a Non O which I already have as married to a Thai woman?

In most cases it is but as said there have been a number of recent reports of issues but often it is not clear on what basis the non immigrant O visa was issued - obviously if retirement it will not be allowed in almost all cases. Your local Labor office that issues the work permit is your best source of current information at that office.