The investigation stems from a drunk driving accident that injured three people on a motorcycle.
The rangers work for the Ministry of Environment, supported by Fauna and Flora International.
Yoeung Baloung, a former police chief of Ratanakkiri province, was supposed to be in jail on charges related to illegal logging.
In 2010, Cambodia produced a milled rice surplus of nearly 2.5 million tons.
Cambodia is hoping to produce 1 million tons for rice for export by 2015.
The $495 million dam, which China Huandian Corporation will control, is expect to produce 338 megawatts by 2015.
The Xayaburi dam is planned in Laos’ northwestern Xayaburi Province, more than 1,000 kilometers upstream from Phnom Penh.
Agriculture contributes more than 30 percent to the GDP and is valued at around $10 billion per year.
Cambodia has an estimated 25 different mineral types, from bauxite to zinc, gold, iron, and gems.
Thailand is the world's largest rice exporter, followed by Vietnam, and Cambodia meanwhile exports about 100,000 tons per year.
Agriculture has emerged as a main economic driver for Cambodia, propping up the country in the wake of the 2008 financial crisis.
A total of four people have died in storms and flooding since Sunday.