Can I work on a Non-B visa without a Work Permit in Thailand, and what happens if I leave my job?

A Non-B visa allows you to stay in Thailand for work purposes, but you must have a Work Permit to legally work. Without a Work Permit, you should refrain from working. If you leave your job, your Non-B visa does not automatically expire; however, you would need to verify your visa status with immigration as your work circumstances have changed.