Canceling a Work Permit in Thailand is free of charge. However, if you have an Extension of Stay based on employment that needs to be canceled, you must go to the Immigration Office with the required letters. If you wish to remain in Thailand after canceling your employment-related extension, you must leave the country by 11:59 PM the same day or you can opt to pay a fee of 1,900 THB for a stamp that allows you to stay an additional 7 days.
Sorry, you only cancel an Extension of Stay based on working in Thailand, if you have the Extension of Stay based on being married with a Thai National you can keep that Extension.
Benjamin ******
Free. If you need to cancel your extension of stay based on employment, you have until 11:59PM the same day to leave Thailand; OR pay the 1,900THB for an extension of stay denied stamp, letting you stay for another 7 days.