I was advised to take Malaria tablets when I went to Cambodia although I was told the risk was low for a short visit to Angkor Wat. If you choose not to take the tablets do absolutely cover yourself with insect repellents especially at night. When I was there there was an outbreak of Dengue fever which is also caused by mosquitos and unfortunately there aren't any tablets that can be taken for this disease. I took both tablets and used repellents. I always think it's better to be safe than sorry.
The best place for info is your doctor.

We have decided to take the tablets whilst we are in Cambodia - Malarone, a bit more expensive but no side effects other than excess wind!!!! and only need to take one day before we enter Cambodia, during the visit and 5 days after we leave. As you say better safe than sorry.