To visit Angkor and other Temples, you need to have an authentic admission pass also called an Angkor Pass. The admission passes are purchased at the main entrance situated on the road to Angkor Wat, and a one-day pass can be found at the another entrance gate on the road from the airport.
A one-day pass costs $20, a three-day pass for $40, and a seven-day pass for $60. A 3-day pass is valid for any 3 days within a week, and a 7-day pass is valid for any seven days within a month. For 3-day and 7-day passes, you need to supply a passport-sized photo when buying the pass. For visitors who have no a photo, they will take their photo for free, but it will take a while if many visitors buy passes.
If you visit Angkor for only one day, you may only be able to take cursory visits to see Angkor Wat and Angkor Thom which are the most renowned temples. A 3-day visit is enough to explore the main temples, and some of the minor sites, and even have some time to explore few other temple sites in depth. A 7-day itinerary give you sufficient time to thoroughly explore all the main temple ruins, visit many of the minor sites, and go to a remote temple site.
You will need to carry your temple pass with you every time you enter the park, and when entering the other temples. Without a valid pass when visiting a temple, or while inside the park, you can be subject to a fine. A daily temple pass isn't needed for remote sites, but some sites have their own admission fees: Phnom Kulen ($20), Koh Ker ($10), Beng Melea ($5).
