@Martyn *****
AND don't believe ANY employer about you needing a Non-B to work. IF you're married to a thai you can legally work and hold a work permit without any issues at all on a marriage extension.
It's just that most employers WANT you on a non-B because that way they have control over your ability to hold the visa. If you're on a marriage extension and lose your job your extension isn't affected at all :O