During my walk outside KKK town I met many Muslims.
The Cham in Cambodia are closely related with Cham of coastal Vietnam. According old tales the first official Muslim envoy to Vietnam and Tang Dynasty in China was sent by the third Caliph in 650. Chinese records proved the theory of the Islam's spread among Cham in the late 10th centuries. After collapse of the Champa Kingdom in 15th century many Muslims moved to Cambodia and Malacca Sultanate.
Champa's exodus lasted all 19th century ( their big community lives in Bangkok ) until Khmer Rouge period. There are some 600,000 Cham Muslims in Cambodia today.