A directive from the Ministry of Cults and Religions states that "Christians are prohibited from visiting people's houses ... knocking on the door and waiting to say 'the Lord has arrived'."
Distribution of religious literature will also be confined to churches, which now must be approved by the ministry before they can be built.
Government officials say while the ruling applies to all non-Buddhist groups, it is aimed at curbing Christian evangelical influence in largely Buddhist Cambodia, amid reports of children being tricked into converting with cakes and free clothing.