It is the only one with a banner in Korean and Khmer bearing the words "Migrant Agricultural Workers' Human Rights Bus," as it plies the narrow roads between farming hamlets and long rows of greenhouses.
The Khmer is targeted to Cambodian migrants, whom Kim was helping on a recent day. South Korean youth in this area are no longer interested in tilling the soil.
Cambodia is South Korea's second-largest source of migrant workers, after China. More than 32,500 Cambodians are in the country on non-professional work visas, mostly doing manual labor on farms and in factories and fisheries. About 222,500 such visa holders are in South Korea.
The country currently allows migrants to fill labor shortages, but soon it may have to allow greater immigration to help augment its aging, shrinking population.
Kim stops at farms and picks up migrants who are not happy with their working conditions. He helps them find new jobs on other farms, and in the process, calls attention to the conditions they face, including unpaid overtime work, makeshift dwellings and no work breaks. Some also complain of a lack of privacy and unwanted physical contact by employers.
Kim says the violation of migrant workers' rights is hard to change because South Korea's immigration system is stacked against them.
"Working conditions are bad and employers are violating the law, but they still manage to hang onto their workers," he says. "The laborers bite the bullet and stay on because they are warned and threatened that if they leave, they can become illegal immigrants."
The issue of migrant workers' rights goes far beyond agriculture. The country's population began to shrink for the first time last year, and the prospect of an aging society looms over South Korea's future.
Chung Ki-seon, a migration expert at Seoul National University, says that South Korea is taking in migrants because it needs to supplement its agriculture, fishing, construction and manufacturing workforce, and not to address a demographic imbalance.
She predicts that situation will change over the next decade, as the country reaches a turning point that will necessitate a policy shift.
"The approximate age of the [Korean] people working the fields right now is over 70," she says. "And once they reach 75 or older, it will be hard for them to remain in the workforce."
But it's very difficult for migrants working in South Korea to become citizens. Chung says the government knows public opinion is against allowing mass immigration. In 2018, a report on the ideal future level of immigration found 42% of South Koreans favored maintaining the current level, while 32% favored a decrease. Just 19% supported an increase.
Korea has long seen itself as a homogeneous culture, not as an immigrant nation or multicultural society. In 2019, just 3.4% of the population was foreign. But demographics leave the government no choice but to allow more immigration, Chung argues, although it doesn't call its policy that.
"Although we call it a 'foreigner' policy, it has all the ingredients of an immigration policy," Chung says. "The foreigner policy contains measures to integrate and recognize immigrants as members of the society, either as citizens or as permanent residents."
The pandemic cut off the inflow of thousands of legally employed migrant workers from Southeast Asia and countries as far away as Pakistan and Uzbekistan. Chung says 5,000 new seasonal laborers were supposed to come into the country to work for 90 days or less last year. But none of them could enter.
As a result, Chung says, "the farms rely mostly on illegal immigrants, who fill 80% to 90% of that shortage." There are more than 392,000 undocumented workers in the country.
The pandemic is making South Koreans more aware of the harsh conditions for migrants who toil on their farms, Chung says.
Last December, the case of a Cambodian migrant who died in a greenhouse that she lived in focused attention on the problem. In response, authorities stopped issuing employment permits to employers who housed their workers in greenhouses and other improvised dwellings.
But the practice continues. Kim, the activist, stops to collect a Cambodian migrant who is still living in a greenhouse, covered with vinyl sheeting. Khen Srey Nuon was living in the greenhouse before the new rule was issued. Her employer claims he offered her accommodation elsewhere but she declined. Even so, she sounds unhappy about her living situation.
Boxes of the strawberries and peppers she harvests and packs sit outside a makeshift bedroom. Her bathroom and kitchen are in separate sheds outside.
"The water here freezes in winter," she says. "My room is also usually freezing. It's difficult to live in. My employer gives me drinking water, but it's not so clean, so I have to buy my own."
At another farm, Cambodian migrant Kuong Srey Leab tells Kim her employers have been deceiving her by requiring her to work for their relatives and friends, something that isn't specified in her employment contract.
"I work hard and it's painful, but I get paid very little," she complains. "I've also worked for my employer's son and his friends, and others whose names I don't even know."
But the employers say that working for relatives is part of the reality of life on family-owned farms. They accuse labor activists, including Kim, of stirring up trouble and undermining what they claim are the generally harmonious relations between migrants and their employers.
"When labor authorities came to inspect, the workers didn't say they had to do any unpaid work," says Yoon Sang-jin, who represents a group of local farmers employing migrant workers. "But they team up with these activists to take advantage of the farmers' difficulties and benefit themselves. We haven't done them any harm."
NPR's Se Eun Gong contributed to this report in Seoul.
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