What should I do if my work permit is canceled but I still have an extension of stay in Thailand?

Decided to write this story as a kind of information sharing. As a visa run operator we face many challenges every day. This story is about a person that had his work permit cancelled in March this year, but kept using the extension of stay valid up to 18 April. He came with us to border on Monday 16 April and Immigration questioned him, he admitted to have stopped working so they refused him to stamp out and ask him to go to Chaeng Watana, pay the fine and to have extension of stay voided. He went to Immigration Chaeng Watana on Tuesday. On Monday he consulted me as well and I said the same, go Immigration , pay the fine, have extension cancelled and than come back to do border run. On Tuesday he did not consult me again, but Wednesday morning he came again, unluckily we had another driver so that driver did not know his story. St the border Immigration remembered him and told him, CAN NOT. He said that Chaeng Watana did not want to cancel his extension as he did not have the cancellation letter from Labor with him, that letter still with Employer. After a lot of phone calls ,etc , we were able to get the copies, etc via LINE and Immigration cancelled his extension, he had to pay the overstay from the day his work permit was cancelled, about 30days, but after that he was able to get the 30 day entry stamp. My message: please follow the rules and have your extension cancelled when stop working, this will safe you a lot of hassle later on.