There is a Chabad House that opened in Phnom Pen in 2009. www.jewishcambodia.com They have Shabbat services and meals, some kosher shelf food for sale, and a nightly Torah study session with dinner.
Cambodia has no Jewish history and there are no Jewish sites, however there are many fascinating attractions to see.
I spent a month in Cambodia prior to the Chabad house being there. I’ve heard a lot of good things about this Chabad including from an old school friend who spent some time in Cambodia helping the Chabad shaliach.
There are a number of Jewish aid organizations that help out in Cambodia, a country that is still rebuilding itself from some very dark times. Between 1975 and 1979, 20% of Cambodians lost their lives. If you do visit Cambodia you will see plenty of books for sale and probably end up watching a movie or two about the Khmer Rouge and the Cambodian genocide.
I found it all interesting because of our own history within the Jewish world and the Nazi genocide we endured. One difference that really disturbed me is that in a way the Cambodia Genocide had an element that that no Jewish genocide ever experienced. In Cambodia kids were given guns, brainwashed, and told to kill their parents. The whole country was killing each other. It wasn’t an outside group killing an inside group, or the other way round.