no you can get a Non O visa based off employment which is then paired with a work permit. If you have the marriage visa then you only need the work permit based on employment.
if you have no idea, it’s better not to give advice. There’s loads of roles. Most western companies hire farangs across all sorts of disciplines, from engineers to sales/marketing to accounting and general management. There really is plenty of opportunities. A marriage visa allows application of a work permit so yes, he has options.
nothing like solid advice from someone who obviously has no idea 🤷🏼♂️. Plenty of job opportunities in Thailand regardless of a degree or if you want to be a teacher. There are some standard jobs which are only reserved for Thais but plenty of jobs for Foreigners also.