Sorry I'm late to this, but echo another easy/successful experience BKK > ICN > USA with tight connection. It was also really late at night and we were groggy.
Even more, my friend broke his toe, was in a wheelchair, and the greeter/escort got him through transit security to the gate without his passport (we were accidentally holding onto it and got separated; and I have no idea how this was possible for him).

There are also nice private bathrooms along the walk, if needed.