Australian officials have visited several sites to accommodate the refugees now on Nauru, including land in Preah Sihanouk province, far from the Cambodian capital where there are few schools, hospitals or other essential services, according to the Phnom Penh Post.
Some islands in the province are owned by wealthy Cambodians connected to key government figures.
Australian officials have also visited sites in Phnom Penh, the newspaper reported.
Amid growing condemnation of the agreement expected to be signed soon, a coalition of 21 key human rights and pro-democracy non-government-organisations issued a statement raising ''serious concerns'' about the reported house hunting and secrecy surrounding the agreement.
The Cambodian Human Rights Action Committee said it is gravely concerned the two countries will push ahead with the agreement without public scrutiny.
Even before the agreement has been signed Australia has sent a Canberra bureaucrat, Greg Kelly, to Cambodia to take charge of the resettlement program and boosted staff at Australia's embassy in Phnom Penh by 10.
''CHRAC is very concerned about the welfare of the refugees who will be settled in Cambodia under this deal,'' the statement said, adding both countries are acting contrary to the fundamental principle of open government, respect for rule of law and due process.
Son Chhay, a leading MP in the opposition National Rescue Party, said he had been told Preah Sihanouk had been considered as a possible location to house some of the refugees.
''I heard (two months) ago that they might be put on one of the islands off Sihanoukville but I wasn't able to (independently) confirm if this is true,'' he said.
''Normally they would look for land owned by a business connected to a government member, encouraged by the Council of Development of Cambodia, so they could profit from it.''
Neither Cambodia nor Australia has made public any details of the agreement that has been condemned by human rights groups, refugee advocates and Cambodia's opposition MPs.
Refugee advocates believe refugees on Nauru will refuse to voluntarily resettle in Cambodia, holding out hope of getting to Australia.
A sticking point in the agreement has been Cambodia's insistence that those coming to Cambodia not be forced.
Cambodia's foreign ministry spokesman Koy Kuong said discussions with Australia were ongoing.
''Since nothing is official we cannot say anything specifically,'' he said.
Cambodia is one of Asia's poorest nations where strongman prime minister Hun Sen has ruled with an iron-fist for decades, often brutally crushing dissent.
Australia is one of Cambodia's largest aid donors, providing more than $329 million over the past four years.