Ok, your TRANSITING from TH to SK to US and they what? Sent you back to TH? How did they even find you? You disembark the aircraft, find your next gate, and board the next aircraft. You never should have even come in contact with customs or security check. Can you give a few more details of your experience? Did they call your name when you landed in SK? Did security meet you at the gate for your connecting flight? Did you provide your jurisdiction the 21 day notice to include transiting airports? More details please. I have an upcoming international trip and I’m trying to see what is going to happen. This is BS if this is happening at TRANSIT airports. Hell, travelling by aircraft might be a thing of the past for SOs.