It is a fact that Angkor Wat and the surrounding temples see an ever increasing number of tourists and large tour groups. There are a few ways to avoid the crowds.
Firstly there are some suggestions on the various times of day, followed by some comments on some specific temples
Angkor Wat is the most popular option for sunrise. But alternatives include Sra Srang and Phnom Bakheng. Sra Srang has many pools and reflections can be seen. Phnom Bakheng is also an good option as you can watch the sun come up behind Angkor Wat – the same attraction as watching the very popular sunset from here.
Most tour groups and many independent tourists take the option of returning to Siem Reap for lunch. This means in this lunch period there are far fewer people about. You can choose to take a lunch with you or even better to choose one of the local spots around the temples.
As described below Phnom Bakheng is overrun at sunset. Remaining in Angkor Wat at sunset on the upper terraces watching the forest views and light changes can be a good alternative. Pre Rup is popular for its rural sunset view over rice-fields. The Western Baray is another spot that has good sunset reflections on its water pools. Phnom Krom or on Tonle Sap lake are also considered to be good at sunset.
Angkor Wat is busiest at sunrise and sunset (6-7am and 3-5pm). While it is busy at sunset it is probably a better option to be here than at Phnom Bakheng where most people go for sunset photographs.
One of the most popular spots for sunset is Phnom Bakheng and it can be a zoo of tourists watching the sun silhouette Angkor Wat. If you do go there it is a walk up the hill and a throng of people at the top. Be prepared for large crowd movements when sunset is judged to be over and people head back down the hill. Some information about being at Phnom Bakheng => Phnom Bakheng at sunset
Bayon is busy all day but often the busiest time is 7;30-9:30am
Banteay Srei’s busiest period is from med-morning through to mid-afternoon as the day trippers arrive and depart.