Modest dress is the rule in Cambodia, particularly for women. Although many tourists wear shorts to deal with the heat, the locals tend to cover as much skin as possible. In Cambodia, shorts are considered proper attire only for schoolchildren!
Men in Cambodia typically wear collared shirts and long pants. Women should not wear short skirts or show their shoulders.
Although tourism has caused this standard to lax somewhat, always dress conservatively when visiting temples, homes, or entering a public office.