As the largest tourist attraction in the country, Siem Reap and nearby Angkor have long ago been de-mined to smooth the way for foreign tourism, so there is no need to worry in this respect. However, some rural areas just outside of the city may not yet have been cleared for mines and unexploded ordinance, so make sure to look out for the warning signs when walking off the beaten path.
Cambodian roads present a risk of serious injury as some of the roads are in need of repair. To minimise the chance of an accident, never ride on a motorbike without wearing a helmet and always exercise good judgment when driving.
Bicycle riders should also take caution but will struggle to find a hire helmet anywhere as they simply don't exist in most places. Pedestrians should be extremely cautious when crossing the road in Siem Reap. Expect motorbike riders in particular to approach from unforeseen directions, often against the flow of traffic.
Crime is not a major problem in Siem Reap but has definitely increased in the past decade as more tourists have come. The problem is mainly as a result of more foreigners hanging around town, which prove a temptation for the odd local when the income disparity is so great. Theft is rarely violent but things can go missing if not looked after properly. Make sure to clutch your bag tightly while riding on a motorbike.