@Andrew *****
sounds lik you aren't changing the type of the visa because you're NOT on any visa, you're on a yearly extension of stay from the immigration office :O
All you'd be doing is changing the reason why you're getting an extension
BUT
know that getting an extension based on employment inside the country takes a WHOLE PILE of paperwork from your employer, the shares of the company, who owns what, the taxes, the employment records of the thais that are employed to offset giving you a work permit, your taxes, pay stubs, withholding documents etc.
If you're wanting an easier way to get a yearly extension rather than the marriage extension I think you're sadly confused :/
It is NOT less paperwork nor is it any easier than the marriage extension you're getting now. AND as people pointed out you already can legally hold a work permit and work here on an extension based on marriage.