BANGKOK: A lack of legal protections is putting refugee children in Bangkok and Jakarta at heightened risk of trafficking and forced labour, campaigners said.

More than 20,000 refugees live in the Thai and Indonesian capitals, many of them children, and neither country is a signatory to the 1951 Refugee Convention, which spells out legal obligations to protect refugees.

That means they are vulnerable to exploitation and abuse and also makes them afraid to report violations for fear of arrest or deportation, said Save the Children's Ratirose Supaporn ahead of the release of a report in Bangkok on Saturday.

"Refugees are vulnerable even before they set off from their home countries, as they are desperate, and often depend on an agent who may dupe them," she said.

"Their insecurity is greater in the host country, where they are often afraid to go out, and are vulnerable to being duped or abused. They are usually too afraid to report any of it, particularly children who are especially at risk," she said.

The Save the Children report comes as the world's attention is focused on the detention of immigrant children who enter the United States illegally with their parents, which has been the subject of widespread criticism.

It said most refugee children in Bangkok and Jakarta were out of school, and many suffered from illness and mental health issues.

Refugees in the two cities cannot legally work and are eventually repatriated to their country of origin, integrated locally or resettled in a third country, the Save the Children report said.

But it warned that refugee resettlement levels are decreasing globally, which means families have to remain in Indonesia and Thailand for longer periods, increasing their vulnerability.

"They (refugees) run out of money, so children may be pushed into working from a young age, and that also raises the risk of trafficking and sexual exploitation," Ratirose told the Thomson Reuters Foundation.

A record 68 million people have been forced to leave their homes worldwide, according to figures the UN refugee agency released this week.

Children make up more than half that number, including many who are unaccompanied or separated from their families.

Rohingya children and others living in refugee camps in Thailand are at risk of being trafficked into sex work, activists say.

Thailand has pledged to develop a screening system for refugees to combat trafficking, and to increase their access to education, healthcare and birth registration. It has also pledged to end the detention of refugee children.

Indonesian president Joko Widodo last year signed a decree that recognises refugees and gives them limited rights.