For those on a Non-B (extension based on employment) is it going to be possible to change jobs within country if you can arrange documents on time? IE having the documents ready, cancelling work permit/extension, and then getting a new extension on the same Non-B with another school/company on the same day? Or, is pretty much everyone in that situation going to need to leave the country, get a new non-b, and come back?
TLDR : Answer Summary
It is theoretically possible to change jobs while on a Non-B visa (employment-based extension) within Thailand, provided that the necessary documents are arranged and timings are coordinated effectively. Both current and new employers must meet immigration requirements and work together to facilitate the process. However, it is advisable to consult with your local immigration office to ensure compliance and to verify if this can be done without needing to exit the country.