While the majority of people flock to Angkor Wat for sunrise, which should be experienced at least once, there are other options. If you are getting a late start and want to avoid the crowds at Angkor Wat, a visit to Bayon Temple for sunrise is a very worthwhile trip.
If you are fortunate to have clear skies in the morning, I would suggest going to the top platform of Bayon and observing the faces as the sun comes up. Part of the fun is finding the right angle and right face where the sun makes first contact. I spent an hour here enjoying the light show on the faces of Bayon. Best part I had the place to my self. No crowds at all!