The three children, a boy of 12, his 14-year-old sister and another girl of 17, have been visited by officials from the North Korean consulate in Vientiane and could be executed for "betraying the party" if they are repatriated.
They were arrested 14 weeks ago crossing the Mekong River into Laos with the intention of continuing on to Thailand and, ultimately, starting new lives in the United States. Their three-month prison sentences have concluded but they remain incarcerated. Police have demanded payments of 500 per child for their release.
"Groups like ours are short of resources and we are very concerned that paying bribes or bounty money could set a precedent that would see Laotian border police hunting down North Korean refugees," said Kim Sang Hun, an international human rights volunteer from South Korea. "500 is a lot of money by local standards."
Hiroshi Kato, the chairman of the Tokyo-based Life Funds for North Korean Refugees, met the children in the prison and said they were "in a panic" after the visit by the North Korean consulate staff, who threatened they would be severely punished when they are repatriated.
"Under North Korea's criminal code, a sentence of 11 years forced labour is possible, although they could also be sentenced to death," he said. That likelihood is increased as the children have already stated they were trying to reach the US, which makes their actions political offences against the party.
Mr Kato was critical of other governments that have failed to intervene, saying the South Korean embassy is only interested in helping defecting party officials or members of North Korea's military, the US refuses to get involved out of fear that it might make the situation worse and Japan's foreign ministry is "awaiting developments."
"I am not sure why the South Korean government is so cool towards this humanitarian issue," he said.
Letters by the three children have been brought out of the prison, with Kim Hyang, 14, pleading, "I am writing this letter as the last chance of a drowning person who will clutch at a straw.
"The North Korean embassy interrogated us and took down all the information on 6 April," she wrote. "We are unfortunate children who came here in search of freedom and are now at risk of losing our lives.
"If any person can give us that freedom, we will remain grateful for the rest of our lives. We can accept anything except going back to North Korea."
Kim's mother died of starvation in 1999 and they were turned out by relatives when the famine worsened before crossing into China in 2002 and surviving by begging. Choi Hyang-mi, 17, fled North Korea with her mother and younger brother after her father's death. Her mother was caught by human traffickers in China and, along with her brother, have not been located.
Choi told Mr Kato that her dream is to become a designer in the US.
Appealing to the government of Laos to release the children into the care of Life Funds for North Korean Refugees, Mr Kim said, "This is not just a case of the life or death of three abandoned children; it is a very grave case of international justice, humanitarianism and international law being challenged by the government of Laos.
"Is the world community going to tolerate such defiance or stand up to uphold justice," he asked.
"We are calling for the strong determination of the international community to uphold human rights and protect refugees everywhere."