Today, the Salt Lake City-based church claims more than 12,000 parishioners in this predominantly Buddhist nation.
That growth has come with a challenge for church leaders, who are now working to encourage fellow converts to engage in what Mormons consider a sacred duty: digging into family history for a Mormon ritual intended to give the dead an opportunity for a better afterlife.
"Most people," said Eng, now the lay leader of a Mormon church in Phnom Penh, "prefer not to do it."
The Mormon preoccupation with family history research is connected to a belief that families can be eternally connected through the practice of posthumous baptism. The rite has stirred controversy in the past: The church has apologized on several occasions in which it was revealed that members performed such proxy baptisms for Jewish victims of the Nazi regime. Mormons now are instructed to only submit for baptism the names of those who are in their own family lineage.
Sophat Yin, who grew up in the western Cambodian city of Battambang during the Khmer Rouge
regime and is now an organizer at the Cambodian Buddhist Society in Fresno, California, is troubled by the proxy baptisms for many of the same reasons Jewish survivors of the Holocaust were. Most of the estimated 1.8 million people killed during the Khmer Rouge's brutal four-year rule in the 1970s were Buddhist. And Buddhist leaders, he said, weren't consulted about the practice. It was just assumed, he noted, that they'd be fine with the same rules as were settled upon with leaders of other religions.
"We Buddhists believe in afterlife, reincarnation and karma," he said. "If I were to die during the Khmer Rouge time, I would ask Mormons to leave me alone."
Still, he said, since he doesn't believe the practice holds any spiritual weight on the souls of the dead, he is trying to not feel offended and trying to look at it as a harmless offered blessing.
In Cambodia, Mormon believers' efforts to baptize family members -- including some of those slaughtered during the Khmer Rouge rule -- have also thus far met with little public backlash. But that might be because, at least for the moment, the work is quite limited.
Samnang Kang, who was recently appointed to work as a family history consultant for church members in Phnom Penh, said last's year's goal was to submit 1,600 names to LDS temple workers in Hong Kong and the Philippines. Parishioners could only manage 1,322.
This year, she said, "we haven't set a goal."
A big part of the challenge is a lack of records. The Khmer Rouge, which occupied the nation from 1975 to 1979, is thought to have destroyed about half of all government records -- the kinds of documents frequently used by Mormons in other nations and which are provided even to non-believers through the church's FamilySearch.org service.
Many more documents weren't specifically targeted for destruction, but were left unprotected during the regime and either looted or ruined by nature, said Khamboly Dy, a staff member at the Documentation Center of Cambodia, which has worked since 1995 to recover and restore the record of the Khmer Rouge's brutal reign.
"It is important to us to collect all the remaining documents and conduct interviews to reconstruct the record," he said.
To that end, the center has recorded conversations with more than 6,000 people -- a tiny fraction of the millions of individuals who survived the regime. But those oral histories are driven by an open-ended questionnaire and don't necessarily include genealogical information that would be helpful to those trying to trace their ancestry.
The center does have what might amount to a treasure trove of information for family history sleuths: As militaries are wont to do, the Khmer Rouge created detailed personnel records for many in its cadres. Center staffers said those records often do include information about soldiers' parents and other family members.
While Cambodian society generally treats Khmer Rouge foot soldiers as victims of the regime, that tolerance is at least partially contingent on a general disinclination to re-examine the past, as opening military personnel files might do. Equally if not more potentially painful: In studying the center's documents, family history searchers might happen upon the name of an ancestor only because another family member gave up that person's name under interrogation or torture.
Local Mormon leaders said they haven't yet asked to look into the documentation center's vaults, though the center's director, Youk Chhang, said he would welcome their queries. He noted that religion, in general, "was the enemy of the Khmer Rouge revolution" and that any avenue "for healing, forgiveness, and moving on" is worth exploring in a nation in which victims and perpetrators of atrocities still live, work and worship side by side.
The center's records potentially could help equalize family history resources in Southeast Asia. The LDS church has managed to acquire an extensive collection of government records from other countries across the region and has published those records on its family history website. However, the site has no historical records from Cambodia.
Paul Nauta, a public relations specialist for the LDS Church who specializes in family history, said even without records "the average person can usually remember three generations back. If you are fortunate to have a parent or grandparent still living, that affords the individual to trace their family history back up to six generations."
But Nauta said only a small set of patrons in Cambodia have listed more than four generations.
Including herself and her children, that's all Vanna Kim has been able to produce. And even at that, she said, "I had to pray for a miracle" that her Buddhist aunt and uncle would help her identify the names of her grandparents.
She's glad to have done her part to build the record base, but genealogy isn't for her. "It was an obligation," she said.
Khoem Samphon, whose written family tree is also only four generations deep, said it isn't just the governmental records that were lost in the Khmer Rouge years. The types of keepsakes many people use to trace back their lineage were often lost, too.
He was 27 years old when the Khmer Rouge swept into Phnom Penh and forced the relocation of millions of people across the country.
"We didn't bring any records with us," he said. "At that time, records were not important. Food was important."
Some of what was left behind -- family photographs, for instance -- are now sold, apparently for souvenirs, at ephemera shops catering to foreign tourists. Some of the pictures have names penciled on the back, but few have any more context than that.
Even if they did, it might not be helpful. Cambodians cycle through family names every few generations, and a lot of people changed their names when the Khmer Rouge came to power to hide familial affiliations.
"Because we were a political family, we did not want anyone to know where we came from," said Sok Mony, whose family didn't reclaim its name until long after the Khmer Rouge had left power.
For a time, during those years, she went by the name Eang Bunna.
"My family kept hiding until 1991," she said, "but my mother wouldn't open up about the past for many years after that."
Cambodians are rightfully proud of their distant past, said physician Lim Keuky, who lives and works minutes away from Angkor Wat, a thousand-year-old temple that draws hundreds of thousands of tourists to Cambodia each year and whose iconic towers appear on everything from the nation's favorite beer to its red, white and blue flag. But, he said, fellow Cambodians -- about 60% of whom are under the age of 30 -- generally prefer to ignore the much more recent past.
"That is why, if you go to someone who is 18 years old and talk about how genocidal the Khmer Rouge was, she would say, 'It's not possible -- you must be lying,' because the parents who lived at that time they don't want to remember," he said. "In trying to forget, then the same thing can come again."
But Lim, the president of the Cambodian Diabetes Association, noted that family history is also important for helping identify those most at risk for diabetes, heart disease and cancer. And increasingly, he added, researchers are demonstrating such conditions may be worse among those whose ancestors suffered traumatic stress, as so many Cambodians have.
"I want to say it strongly -- I cannot say it strongly enough -- that Cambodians must work to remember the past," Lim said.
Eng, who last year was appointed as a stake president to lead a new church by his home, said he also is hopeful his fellow Cambodians will wake up to the importance of learning about their family history, and not just for the purposes of Mormon rituals.
Logging into a computer at the church, he called up his family history profile on the genealogy website. Soon he was face to face with a black and white photograph of his father.
"You see," he laughed, "he is handsome like me."
Eng understands why Cambodians are hesitant to dig into their family roots; he was a member of the LDS church for more than a decade before he began to do so.
But now, Eng said, he'd like everyone to have the same experience he had once he began looking for long-lost relatives.
"When I would work on finding relatives," he said, "I pulled out my dad's picture and it felt like he was close to me again."