Non B Extension Stay Cancellation Question, Please Help!

Hi Everyone, 

I'm sure this questions has been raised many times, but I just want to get latest update. Maybe you will find this is a different case, so I will really appreciate if anyone fully informed or knowledged able help. 

My husband is Indian, he has valid work permit and the non B extension till 10th August'19 from Pathum Tani (because his head office over there) but he works in Bangkok branch. He is resigning already and last working will be end of this month as he got another job offer. He plan to surrender work permit only on his last day, as the company will cancel it for him later on and he will straight go to Nong Khai immigration to cancel the extension as he want to visit laos first and fly back to India from there to get new Non B Visa. My questions are;

1. Is it possible for him to cancel his extension in Nong Khai since he is Indian, the immigration know Indian can't do any visa in Laos, will they question him why exit from nongkhai??is there ever Indian crossing out from there?

2. Is the termination letter or employement letter only enough to cancel it?as it will be wasting time if he cant do it there with that document only.

3. We know it will be much easier to just fly out from Bangkok, but he doesnt want any issue for future extension when he's coming back to Thailand with fresh non B, if he doesn't cancel it.

Thanks alot!!