Number 1: Swim with friends. Take advantage of that salted pool because there's no beach in Siem Reap. Nearest is Sihanoukville which takes around 8 hours of road travel.
Number 2: Hire a tuktuk and go around to check out nearby tourist spots in town like museums, old markets and temples.
Number 3: Go shopping! For affordable souvenirs, check out the old market.
Number 4: Chill at The Blue Pumpkin. It is a french bakery and patisserie, an ice cream parlor and a restaurant with a lounge atmosphere. They also have free WiFi!
Number 5: There are a lot of bike rentals available in Siem Reap for as low as USD2.00/day. Instead of taking the tuktuk or van, why not ride a bike all the way to the temples? It takes around 20-30 minutes one-way. Ok na ok as exercise! Lucky for us, we got to use the bicycles of Angkor Heritage Boutique Hotel for free! ;)
Number 6: Last but not the least, get your $20 (1-day) Angkor Pass in the afternoon. Angkor Passes issued after 5:00PM are valid for use until the next day. Perfect for those who want to see both the sunrise and sunset in Angkor Wat Temple.