You should be fine assuming you're arriving on a domestic service, your inbound is no more than 30 minutes late, and that you're ticketed straight through and don't have to check in again at SQ.

The UA domestic terminal is about ten minutes' walk from the international terminal. At that time of night take the stroll rather than the shuttle bus; it'll be nice and you'll be glad of the air and the stretch. Exit the UA terminal and turn left; the international building is up where the access road curves.