Around 300 families lost their homes in the Jan. 3 forced eviction of Borei Keila.
An estimated 20,000 Cambodians are trafficked throughout the region each year.
A UN spokesman said the organization was “aware of this development” but declined to comment further.
A US Embassy spokesman confirmed Baer had met with government and opposition officials, but declined to elaborate.
Cambodia and other Asean countries have adopted a draft of a charter for human rights that will see rigorous debate next month.
The site, at Phnom Bath mountain, is 50 kilometers outside the capital and lacks clean water, electricity, and health care facilities.
Prime Minister Hun Sen has said there will be no political deal and that Sam Rainsy’s cases are matters for the courts.
Campaigning for the Senate election, which is held for representatives of eight regions, will go from Jan. 7 to Jan. 27.
About 13,000 political officials of the Cambodian People’s and Sam Rainsy parties will vote in the election.
Moek Dara is accused of abusing his post to gather hundreds of thousands of dollars in bribes and organizing drug trafficking.
According to Adhoc, there are more than 15,000 prisoners nationwide in a detention system that cannot hold them.
The Mekong River Commission was made in 1996, a year after the inception of the 1995 Mekong Agreement.