She can't imagine life in the two-storey French-colonial house behind high grey walls, where the Australian flag hangs limply in the sticky heat of late afternoon.

On a good day Srey Kuoch earns $5 providing sex for mostly Khmer men who prowl the park around historic Wat Phnom, a tourist attraction that for years has also been a centre for sex workers, drug users and beggars.

Now 25 and holding her three year-old son Chan Vutha, who has no pants, Srey Kuoch says she would like to quit her life as a sex worker and buy a street cart to sell coffee and soft drinks.

But she points to the needle scars on her arms. "I don't feel right without heroin … I need to spend the money that way," she says.

Earlier this year Srey Kuoch learnt she is HIV positive, like many of the hundreds of Wat Phnom's sex workers who play a cat-and-mouse game with police when they arrive in trucks to take them away to detention centres, where they say they are often mistreated.

"I am careful now. When I went with a customer a few months ago my son was lost for four days," she says. "He was found near a market with a lacerated leg and bruises all over his body. I don't know what happened to him but when I got him back he cried all the time."

Sou Sotheavy, a 76-year-old transgender social worker and survivor of the Khmer Rouge genocide, brought Fairfax Media to the park to meet Srey Kuoch because she is angry that Australia plans to send refugees to Cambodia, a country where, she says, the government cannot look after its own people.

She says she empathises with the refugees as she listens to news of Australia's controversial plan on Radio Australia.

Sou Sotheavy was among Cambodians marched from Phnom Penh by the murderous Khmer Rouge in April 1975.

She spent the following three years as a refugee, forced to move from province to province, singled out because of her effeminate behaviour and often raped and brutalised.

"I know what it is like to be shunted from place to place as a refugee," she says. "There is no safety net in Cambodia … no social welfare, no pensions, no healthcare, little education for most of the people," she says.

"Most Cambodians struggle to earn a $1 a day. Australia has a safety net and the refugees must be allowed to go to there."

Sou Sotheavy's stand is backed by most of the non-government organisations in Cambodia, which have issued joint statements condemning Australia.

A coalition of 21 organisations working to promote human rights in Cambodia on Friday described the plan as a cynical attempt to place refugees who had already suffered persecution in their home countries and harsh detention in Australia into further hardship in Cambodia.

Amnesty International called the plan a new low in Australia's inhumane treatment of asylum seekers. The plan is also opposed by the United Nations refugee agency UNHCR, which only has a small office in Cambodia and was excluded from negotiations that led to Immigration Minister Scott Morrison signing the agreement in Phnom Penh on Friday.

"Think about the refugees … they cannot speak Khmer. There are no jobs for them. They will have no land. They will not understand the culture," Sou Sotheavy says, adding that if they are given special treatment that will be unfair to impoverished Cambodians, and could cause trouble in communities.

Mr Morrison says the refugees who attempted to reach Australia by boat are "quite innovative and entrepreneurial and I think there would be opportunities for people with those sorts of skills and enthusiasms" in Cambodia.

He says "support will be tailored to the needs of those as part of a package of measures that will go to their resettlement, which is designed to make them self-reliant as quickly as possible".

Many countries, including Australia, have people like Srey Kuoch in dire need of help but no-one has to look far in Cambodia to see chronic disadvantage in the country still recovering from years of civil war and a genocide where an estimated 1.7 million people died from starvation, execution and disease.

Families are living in Phnom Penh slums under tarpaulins. Others scavenge on rubbish dumps. Vulnerable children beg before tourists on Phnom Penh's riverside.

In rural areas most of the people live a hand-to-mouth existence and while the country has made economic progress, it still struggles to provide adequate services in areas such as health and education.

Cambodia is ruled by a regime considered among the world's most corrupt despite receiving hundreds of millions in foreign aid, including an additional $40 million from Australia over the next four years in return for the country taking refugees.

Cambodia's government, ruled by strongman Hun Sen, has a long history of playing politics with refugees and using them as bargaining chips in bilateral relations with countries such as Vietnam and China.

The most prominent case was in December 2009 when Cambodia forcibly returned 20 UN-recognised Uighur refugees to China and then a few days later collected a huge aid package from Beijing.

Sixty refugees already in the country want to leave and would be destitute if they were not receiving support from organisations such as the Jesuit Refuge Service.

Cambodian officials have made clear that any refugees who arrive will be forbidden from engaging in politics connected to the country from which they fled, a violation of refugees' civil and political rights.

Cambodia has not taken steps to deal with what rights advocates say is the serious discrimination and deprivation of rights of ethnic Vietnamese, some of whom have lived in Cambodia for generations yet are still stateless without access to basic government services.

"The Hun Sen government severely restricts the rights and freedom of expression, assembly and association and state security forces routinely commit killings, torture and other abuses with impunity," Human Rights Watch says. "Those living on the margins – including refugees and asylum seekers lacking employment, Khmer language skills and social network – are at particular risk," the New York-based organisation says.

"For instance, Human Rights Watch has documented the arbitrary arrest, detention and mistreatment of undesirables housed in squalid detention centres run by the Social Welfare Ministry, where beatings, torture and rapes by guards go unpunished."

Defending the decision of his government, Mr Morrison says Cambodian poverty has fallen from more than 50 per cent to around 20 per cent. "I mean this is a country that is trying to get on its feet; this is a country that is making great progress," he says.

Mr Morrison noted that Cambodia's population has doubled from the dark years of the Khmer Rouge period.

He said that rather than keep the country isolated, the rest of the world should give them a chance to do positive things such as co-operating with Australia on the resettlement plan.

"We say we should give them a go," he said.

Sou Sotheavy, who is also HIV positive and runs her own organisation to help sex workers, says she fears the refugees will not survive long in Cambodia after they receive Australia's initial help to resettle.

"Australia has abundant resources while we have few … this is difficult for me to understand," she says.