Originally Posted by A_Lee

There is nothing physically stopping an international transit passenger from leaving the airport at BKK once they arrive from CNX, unless some personnel notices the sticker and tries to stop you. If they don't notice, or you take it off, you can easily exit through the domestic arrivals. Then what happens after that, I do not know, but if they said you reentered Thailand, I can see them asking you to pay the departure tax again (meaning you paid it once already as part of your ticket departing from CNX, and you may need to pay it again for departing from BKK). If you just make up some excuse that you got lost and went the wrong way, I don't know what they'd say. But if you stayed outside for several hours and then tried to use that excuse, they'd probably figure out you were lying.