I recently posted asking about when leaving Chiang Rai on a flight ticket going abroad and stopping off in Bangkok, where I would go through immigration , whether there was in immigration at CR airport . The conclusion was that there is immigration at CR airport , but I didn't go through immigration at CR . I got stamped out in Bangkok . Had I got stamped out in CR , I could have just walked back into Thailand on arrival . So, I think that direct flights abroad get stamped out in CR and BKK stopover flights get stamped out in BKK