North Koreans have toiled and slept at construction sites in Mongolia, they have operated cashmere sewing machines, and their acupuncture skills are highly prized in one of the few democracies employing them.
But the nearly 1,200 North Koreans living in the country wedged between Russia and China must now pack their bags as Mongolia enforces tough United Nations sanctions severely curbing trade with Pyongyang.
The UN estimated in September that 100,000 North Koreans work abroad and send some $500 million in wages back to the authoritarian regime each year.
But the UN Security Council ordered nations to stop providing guest worker permits to North Koreans after Pyongyang detonated its most powerful nuclear bomb.
The US is now pushing for more sanctions after the regime tested another intercontinental ballistic missile in late November.
North Koreans have to leave Mongolia by the end of the year as their one-year work authorisations will not be renewed, the labour ministry said.
"Private entities will not be able to offer new contracts due to the UN resolution. Mongolia has been following every part of the resolution," Shijeekhuugiin Odonbaatar, a Mongolian foreign ministry official, told AFP.
The number of North Koreans working in Mongolia has dropped every year since peaking at 2,123 in 2013.
There were 1,190 North Koreans employed in the vast country of three million people as of November -- often under murky work and living conditions.
Most of the North Koreans who work abroad are in China and Russia, but they have also been found elsewhere in Asia, Africa, Europe and the Middle East.
Across the world, they work 12-hour to 16-hour days, with only one or two days off per month. The North Korean government takes between 70 and 90 percent of their monthly wages, which range from $300 to $1,000, according to the US State Department.
Some 150 North Koreans have left Angola. In Qatar, the contracts of some 650 construction workers will expire next year. Poland, where as many as 500 have laboured, will not renew work permits.
The head of a Russian parliamentary delegation visiting North Korea this week said "everything" must be done to allow those who have already received work permits to finish their jobs in Russia, where an expert estimates around 30,000 live.
In Mongolia, construction companies have hired North Koreans for their reputation for working long hours without complaint.
They live in toolsheds of construction sites or in the basements of apartment projects. They never take time off or even leave the construction sites as they are not allowed to wander in the city on their own.
In September, a 27-year-old North Korean worker died after falling from an apartment in a residential complex under construction in Ulaanbaatar.
At the fenced-off site, AFP journalists saw three toolsheds with a clothes line strung between them. The workers angrily refused to talk to the reporters and tried to grab their cameras.
A South Korean Christian activist who has sought to help North Koreans said he wished that Mongolians would do more for those who work in poor conditions.
"In winter most of them live in the basement of the building that they are building. There is no heating in that unfinished building," he said, speaking on condition of anonymity.
"Unfortunately, it is too risky for South Koreans to help those workers directly. I used to help some of construction workers in the past, through one man. But one day, that man just disappeared. I never saw him again."
Conditions at Mongolia's garment factories have also faced scrutiny.
But more than 100 North Koreans left Gobi Cashmere, Mongolia's biggest cashmere factory, after their contracts ended in August.
"We hired North Koreans because of a lack of Mongolians skilled in operating garment machines," the company's lawyer, Tsogtbayariin Tsaschiker, told AFP.
"The South Korean press publishes false stories that the companies pay North Koreans with shirts, not money. We paid them exactly the same salary as we pay our Mongolian workers and they work eight hours like the Mongolian workers. They used to receive their salary through Mongolian banks."
North Koreans are also renowned for their skills in traditional Korean medicine, including acupuncture and chiropractic care.
The facilities send their salaries to the North Korean embassy, which then pays the staff. The embassy declined to comment.
The acupuncturists and chiropractors have better conditions than the construction workers as their food and apartments are provided by the clinics.
Sunjidmaa Mitiya, chief doctor at Sky, a private traditional medicine hospital, said her two North Korean employees attract many customers.
"Patients always have high satisfaction with their treatment and more patients come to our clinic thanks to the good results see by other clients," Mitiya said.
"They work from their heart, and they are happy to work in Mongolia," she said. "The previous doctor... begged the clinic to hire him again after his contract ended."