In my subjective and casual observation of some Cham Muslim communities in southern Cambodia, over the past decade the number of Cham women and girls donning the veil has risen from well less than half to a nearly universal practice.
The Cham are an ethnic minority group in Cambodia, distinct from the Khmers. They represent the remnants of the Kingdom of Champa, formerly located in what is now central Vietnam. Champa's history stretches into prehistory, but the kingdom was worn down over centuries of war and finally extinguished by the Vietnamese in the early 19th century. Originally Hindu like the Khmers, most of Champa converted to Islam in the 16th-18th centuries. Survivors of the fall of Champa fled Vietnam, scattering into Cambodia where they were granted refuge and settled in pockets, often along waterways. Several Cham Muslims communities dot southern Kampot province, clustered into certain areas, many hugging the rivers of the coastal area. The main road from Sihanoukville to Kampot (NR3) and on to Kep (R31) passes through many Cham communities, sometimes marked by the presence of a mosque or Arabic writing alongside the Khmer on school signs.
The different ethnic communities can also be distinguished by the dress of the people. Cham men often, perhaps even usually wear a sarong and taqiyah. The women wear sarongs as well. But their use of the hijab has changed significantly over the last decade. To my memory,10 or 15 years ago it was largely for the matronly and older women, similar to the practice of Khmer women wrapping their hair in a krama (a traditional checked Khmer scarf.) A couple of the most distinguishable differences between the two different ethnic groups was the somewhat different way the women draped their headwear and the pattern of the fabric - Khmers universally wearing the traditional checked pattern krama whereas the Cham women often use non-checked patterns and solid colors. Back then some younger Cham women also wore the veil but not as a rule, and it was rarely seen on children.
These days, in 2011, the hijab seems almost universal as I drive through and by Muslim communities along Route #3 in southern Cambodia. It is worn by women, girls and very often children, usually in distinctive traditional hijab styles. And, for the first time, in the last year or so I have seen a couple of women in full cover dress in Kampot province. The surface differences between the Khmer and Cham communities is no longer a subtle one.
A few related links:
Cambodian Muslim women dropping out of state schools - 2007
Cambodian prime minister tells schools to allow Muslim headscarves - Sept 11, 2008
Islam in Cambodia
An American Mosque in Cambodia
Phnom Penh Post: Concern over radicalization - July 14, 2011