On a recent morning, 21-year-old North Korean waitress Ri Suhyang fled the restaurant where she worked, leaving her passport and iPhone 4 behind. Around the same time, across town, a middle-aged South Korean tour guide walked out on his wife and children.

Neither has been seen since.

The incident, which began with a quiet word in Pyongyang Friendship Restaurant and led to a cross-border flight to Thailand, has shocked the community of North and South Koreans living side by side in Siem Reap.

“There was a nice Korean man, they fell in love together, and they left,” said an official familiar with the case, a couple of weeks after the May 13 disappearances.

“North Korea doesn’t allow that kind of love. But in South Korea? Why not? The story is romantic and a little tragic, a little political.”

Pyongyang Friendship Restaurant is a nondescript one-storey building on Siem Reap’s National Road Six. Lined with kitschy hotels and massage parlours, the highway has the desolate feeling of any airport road.

But if Cambodia has a Little Korea, this is it. On the main drag as well as backstreets and residential areas, Korean letters signpost dozens of barbecue and noodle joints, mini-marts and churches. A decade ago, little was here.

In 2006 there were about 25 Korean restaurants in the city. Now there are close to 70, catering to about 1000 South Koreans who live and work in the gateway town to the Angkor temples.

A few hundred are tour guides, permanent and seasonal. Leading largely separate lives from the locals, some of the people they come in closest contact with are their cousins from the secretive North. At two North Korean owned and operated restaurants, Pyongyang and Pyongyang Friendship Restaurant, citizens of both sides of the border meet, snap photos and talk about anything but politics.

Part of a worldwide chain that generates hard currency for the regime, the outlets are known for naengmyeon, or cold noodles. But the biggest draw is the 20 doll-faced waitresses who double as performers, playing music and twirling like spinning tops in billowy costumes. They are among an overseas North Korean workforce formed in the 1980s and expanded since the mid-2000s, according to Sheena Chestnut Greitens, a senior fellow with the Center for East Asia Policy Studies at the Brookings Institution.

Jang Song-Thaek, the uncle of leader Kim Jong-Un, is believed to have played a part in running the workforce, established in countries from China to Amsterdam, who pay their own expenses and make gifts to the centre. The role may have contributed to his execution in December.

“In any dictatorship, it’s dangerous to be someone the leader depends on to stay in power – it means that you can easily become a threat, as it appears that Jang and the patronage system that he ran did,” wrote Greitens in an email.

Since his death the military has taken over, according to a defector with sources in the country who spoke on condition of anonymity.

In the early days, workers were sent abroad as a punishment, but the jobs became more desirable as access to hard currency at home grew increasingly important.

“Today, many of the workers who participate are people who have at least enough money and political connections to offer bribes to get these opportunities,” explained Greitens.

The waitresses usually hail from privileged families or ‘good songbun’ in the North Korean class system, often associated with the government and core elite. All college-educated, most have gone to a performing arts school and complete intensive training before they are allowed to leave.

Once overseas, they can earn a small salary, $95 per month according to an official, passing extra to the boss who keeps their passports. They are kept under constant surveillance and are forbidden to leave the restaurant except occasionally in groups.

“I saw them in the Apsara Hotel swimming pool once,” said Kim Sang-Hun*, a prominent local businessman. He compared the regimented outings of the waitresses to those of an army. “They were amazed, ‘wow, sometimes it’s bright’, they said.” Some of the women working in the Cambodian outlets have attracted fame on South Korean blogs and websites, and theories about their true identities abound. Local businessmen believe they are spies. “I heard they are trained in martial arts,” said Sang-Hun.

Not that it stops the tour guides from visiting the restaurant, both on and off the clock. “Most of them are young guys and there are young beautiful women,” he added.

“Sometimes they make personal relationships, and come in again after work. The manager is not happy about that.”

Shortly after seven on a recent evening, Pyongyang Friendship Restaurant was empty. A crowd of waitresses in flowery orange dresses sat at tables, paintings of peasants and snow-white terriers on the walls behind them. One strummed a guitar. The others were glued to a television showing what looked like a North Korean drama: a woman in a black cowl walked on a snowy mountain trail. When asked whether the films came from Pyongyang, the waitresses gave an enthusiastic nod.

It was here that Ri Suhyang, a talented drum player, arrived a year ago, joining a staff of about 20, all of who all live and work on the premises. Most stay two years but some have their contracts extended for one final year. If they make a mistake, which range from failing to give tips to the boss to talking too much to a foreigner, the waitresses will be sent home. Suhyang is believed to have slipped up and been faced with a choice: be deported to North Korea to a re-education or political prisoner camp, or flee. The hermit kingdom takes a dim view of defectors who, if caught, are treated brutally.

“She told the boss that she was going out for a while and then she didn’t come back,” said Chao Mao Vireak, immigration chief of the Siem Reap police, who declined to give details.

The deputy manager of the restaurant who would not give his name said he was under no obligation to answer questions. But the South Korean embassy confirmed they believe the couple to be safe in Thailand. According to officials and members of the local community, her companion is Park Seong-Min*, a 39-year-old tour guide who had lived in Siem Reap for years. A father of several children, he was well-known and respected.

While Seong-Min was a regular customer of Pyongyang Friendship Restaurant, some doubt that he would have been in a relationship with the waitress. His wife is believed to have recently given birth.

“I don’t think they love each other,” said a representative of the South Korean Association in Siem Reap who asked not to be named. “I know he loves and takes good care of his family.”

Shortly after Seong-Min went missing the North Korean authorities turned up at his home asking questions and within a few days his family left. The tour guide could face arrest if found. In 2012, a waitress, Mun, went missing from one of Phnom Penh’s North Korean restaurants, taking a South Korean man only referred to as Kim with her.

She escaped to Thailand, which, unlike Cambodia, has vowed to allow defectors safe passage to the South. Kim, who had fled the North himself, spent 130 days in jail after being accused of kidnapping.

The representative of the South Korean Association in Siem Reap said Suhyang’s manager had visited Seong-Min’s travel agency and threatened to pursue trafficking charges unless the guide surrenders.

The future looks uncertain for Suhyang and Seong-Min. The North Korean regime is known for severely punishing the families of defectors.

In Siem Reap, North and South Korean life seems to have carried on, albeit with a hint of tension

At Pyongyang restaurant, a female manager looked startled and pointed across the road towards the sister outlet when asked about Suhyang.

At closing time, two South Koreans stumbled out of the Pyongyang Friendship Restaurant as a gaggle of waitresses leaned through the doorway in an absurd pose, eyes wide and mouths popped open like fish out of water. All were accounted for but one.

* Names have been changed to protect identities.

Poppy McPherson is the Post Weekend Features Editor. Additional reporting by Thik Kaliyann.

Read a Q&A with Greg Scarlatoiu, executive director of the Committee for Human Rights in North Korea, on the conditions and controls North Koreans working abroad in these circumstances face.