City officials could not be reached for comment, but rights workers said they expect the 13 detainees will appear in court Wednesday.
Authorities say they want to arrest Bun Ratha for participating in an anti-government movement, alongside other suspects in Kratie.
Two demonstrations—one of factory workers and one of displaced city residents—were held on Monday.
Security forces have left a village in Kratie that was the site of the shooting death of a teenage girl by government forces last week.
The ultimate goal is to have libraries in all of Cambodia’s 26 prisons by 2014, serving more than 15,000 prisoners nationwide.
The delegation also met with UN officials in New York last week and were scheduled to talk with the US State Department Friday.
Those arrested were Khat Sovann, 54, Pum Vannak, 53, Pon Soeurn, 34, and an unnamed fourth suspect.
Rights workers estimated between 400 and 1,000 villagers in Broma village, Chlong district, were set to be evicted.
At least 10 parties have registered for elections, which will be held across 1,633 communes next month.
Family members say Chan Samnang died because of exposure to poor living conditions at a relocation site outside the city.
An attorney for the three women, called the summons “a good opportunity” that would allow the women to “tell the true story."
Villagers say they have been pushed off nearly 1,500 hectares of land to make way for the senator’s sugar cane crops.