I am a British national currently in Bangkok on a Non B visa with an extension of stay based on work until August. I plan to leave my job in a few months and cancel my work permit. I wish to remain in Thailand without exiting by changing my reason of stay. I wish to change this to be based on marriage. Firstly can this be done? Secondly can this be done at the time that my work permit is cancelled or does it need to be done in advance? Does the required 400K need to come from abroad? Thank you for your advice.
TLDR : Answer Summary
Yes, you can change your Non B visa to a marriage visa after canceling your work permit. You will need to cancel your work permit with a letter from your employer confirming your departure. Then, you can apply for a marriage extension at the immigration office within 7 days. The required 400,000 THB does not need to be transferred from abroad, but it should be held in your account for at least 2 months before applying.