What is the process for a teacher in Phuket to transfer their work permit and extension to a new job in Bangkok without leaving Thailand?

Do they have a permanent teacher’s license (5 year) from Kurusapa? If not, it may be difficult for the new school to prepare the paperwork in time. Those who use the 2 year temporary teaching licenses are the ones who will have a problem. That document sometimes takes weeks. If the new school is attentive, they may be able to do it. But, usually they are not proactive enough.

Things to consider.

BOTH employers need to work together AND he would need to cancel the current extension with documentation from the employer at the immigration office that he uses now, GO to the new immigration office and apply for a new extension with documents from the new employer.

He can cancel an extension early at his current employment (go a week or so before his last day and they will stamp him in until that date) then he'll have time to go to the other immigration office with documents from the new employer to apply for the new extension.

because he's using two completely different immigration offices I'd say he should go and talk to them both before he tries to pull it off. It CAN be done, BUT he's gonna hafta really have his shit together to make it work. There's not much room for error, it either works or he will have to leave :/