Islam is the religion of a majority of the Cham (also called Khmer Islam) and Malay minorities in Cambodia. According to Po Dharma, there were 150,000 to 200,000 Muslims in Cambodia as late as 1975. Persecution under the Khmer Rouge eroded their numbers, however, and by the late 1980s they probably had not regained their former strength. Today, there are an estimated 500,000 Cham Muslims in Cambodia, or roughly 3% of the total population of Cambodia. All of the Cham Muslims are Sunnis of the Shafi'i school. Po Dharma divides the Muslim Cham in Cambodia into a traditionalist branch and an orthodox branch.

The Cham have their own mosques. In 1962 there were about 100 mosques in the country. At the end of the nineteenth century, the Muslims in Cambodia formed a unified community under the authority of four religious dignitaries--mupti, tuk kalih, raja kalik, and tvan pake. A council of notables in Cham villages consisted of one hakem and several katip, bilal, and labi. The four high dignitaries and the hakem were exempt from personal taxes, and they were invited to take part in major national ceremonies at the royal court. When Cambodia became independent, the Islamic community was placed under the control of a five-member council that represented the community in official functions and in contacts with other Islamic communities. Each Muslim community has a hakem who leads the community and the mosque, an imam who leads the prayers, and a bilal who calls the faithful to the daily prayers. The peninsula of Chrouy Changvar near Phnom Penh is considered the spiritual center of the Cham, and several high Muslim officials reside there. Each year some of the Cham go to study the Qur'an at Kelantan in Malaysia, and some go on to study in, or make a pilgrimage to, Mecca. According to figures from the late 1950s, about 7 percent of the Cham had completed the pilgrimage and could wear the fez or turban as a sign of their accomplishment.

The traditional Cham retain many ancient Muslim or pre-Muslim traditions and rites. They consider Allah as the all-powerful God, but they also recognize other non-Islamic practices. They are closer, in many respects, to the Cham of coastal Vietnam than they are to other Muslims. The religious dignitaries of the traditional Cham (and of the Cham in Vietnam) dress completely in white, and they shave their heads and faces. These Cham believe in the power of magic and sorcery, and they attach great importance to magical practices in order to avoid sickness or slow or violent death. They believe in many supernatural powers. Although they show little interest in the pilgrimage to Mecca and in the five daily prayers, the traditional Cham do celebrate many Muslim festivals and rituals.

The orthodox Cham have adopted a more conformist religion largely because of their close contacts with, and intermarriages with, the Malay community. In fact, the orthodox Cham have adopted Malay customs and family organization, and many speak the Malay language. They send pilgrims to Mecca, and they attend international Islamic conferences. Conflicts between the traditional and the orthodox Cham increased between 1954 and 1975. For example, the two groups polarized the population of one village, and each group eventually had its own mosque and separate religious organization.

According to Cham sources, 132 mosques were destroyed during the Khmer Rouge era, many others were desecrated, and Muslims were not allowed to worship. Later, since the Vietnamese-installed PRK regime, Islam has been given the same freedom as Buddhism. Vickery believes that about 185,000 Cham lived in Cambodia in the mid-1980s and that the number of mosques was about the same then as it was before 1975. In early 1988, there were six mosques in the Phnom Penh area and a "good number" in the provinces, but Muslim dignitaries were thinly stretched; only 20 of the previous 113 most prominent Cham clergy in Cambodia survived the Khmer Rouge period.

Source : http://en.wikipedia.org/wiki/Islam_in_Cambodia