VIENTIANE, Laos -- He was last seen driving home in his old, rusty jeep. And then he vanished.
The disappearance nearly one month ago of Sombath Somphone, a United States-trained agriculture specialist who led one of the most successful nonprofit organizations in Laos, has baffled his family and friends and raised alarms that a nascent liberalization of the Communist-ruled country could be sliding backward.
Mr. Sombath, 60, who won many awards for his public service, was known to be nonconfrontational and adept at forging compromises with the authoritarian government of Laos.
"We have no malice against the government," said Ng Shui Meng, Mr. Sombath's wife, who is from Singapore and met Mr. Sombath while they both studied in the United States. "We want to live our lives quietly."
The disappearance has set off an enormous campaign by Mr. Sombath's large network of friends and aid workers across Southeast Asia who know him from his development work. The campaign has put Laos, an obscure country run by an opaque Communist party, under increasing pressure to provide answers.
The country has taken halting steps to modernize its one-party system in recent years but has also cracked down on dissent, and its security services have been linked to a series of politically motivated assassinations in neighboring Thailand.
Paradoxically for the Lao government, it is a network of cameras that the municipal police installed over the past three years to monitor "anti-social behavior" that have pointed to signs of the government's involvement in Mr. Sombath's disappearance.
Helpful workers at a local police station initially showed the family images of Mr. Sombath's jeep stopped at a police checkpoint on the evening of Dec. 15. Mr. Sombath then appeared to be driven off in a white vehicle.
Family members had the presence of mind to record the footage with their own digital devices -- crucial because the government now refuses to let them view the video again despite pleas by diplomats who would like to analyze it for clues like license plates. (The video is now circulating on YouTube and is also available at sombath.org, a site put up by Mr. Sombath's friends and dedicated to tracing his whereabouts).
Since the search for Mr. Sombath began, the Lao government has issued only short statements that suggest, without offering details, that he may have been involved in a personal dispute. But those following the case closely remain unconvinced.
"The bottom line is that we haven't heard anything beyond a brief statement that doesn't clarify anything," Karen B. Stewart, the U.S. ambassador to Laos, said in an interview. "There's been no full report about the status of the investigation or whatever is going on."
A mountainous and landlocked country of six million, Laos is often portrayed in guidebooks and tourist brochures as a gentle land of stilt houses along the Mekong River, smiling and easygoing rice farmers, Buddhist monks and village silk weavers.
But the contrast to these placid images is a Communist party, formally called the Lao People's Revolutionary Party, that crushes anything deemed to be a threat to its monopoly on power.
"There's a nostalgic picture of women in their wraparound skirts, a beautiful country with tourist attractions," said Adisorn Semyaem, an expert on Laos at the Mekong Studies Center at Chulalongkorn University in Bangkok. "That's not the total picture. There's also another side of the coin."
A precise accounting of repression in Laos in difficult to obtain because the news media are controlled by the government and communication is poor across the impoverished countryside. But one measure of politically related violence can be found when it spills over into the country's freewheeling neighbor, Thailand, where it is recorded by the police and reported in the news media.
Mr. Adisorn, who has researched Lao politics for the past two decades, has compiled a list of more than 20 Lao citizens assassinated in Thailand over what appear to be political reasons, including a Buddhist monk who opposed the government and a member of the former Lao royal family. The crimes all remain unresolved.
Inside Laos, the government periodically arrests members of Protestant Christian religious groups, farmers who complain that their land had been taken away and anyone else whom they judge to "have political agendas," Mr. Adisorn said.
Mr. Adisorn has an extensive network of contacts inside the Lao government and has been asking about Mr. Sombath's case. "I assume that he is still alive but that the government is finding it very difficult to find a way out of the situation," he said.
An official who answered the telephone at the Lao Foreign Ministry advised a reporter to monitor the Lao press for updates on the case and said a spokesperson was not available.
There is a troubling precedent for a politically linked disappearance. In 2007, Sompawn Khantisouk, the manager of an ecotourism guesthouse who was outspoken in his criticism of Chinese-owned plantations in the north of the country, disappeared and has not been seen since.
If Laos has avoided the same level of scrutiny of other authoritarian countries in the region, it is partly because the political oppression is hardly visible to outsiders when they visit. The center of Vientiane has lively, outdoor restaurants and countless small hotels and tourist shops.
The country received a record 3.1 million foreign visitors last year -- equivalent to half the population -- according to the government, which promoted 2012 as Visit Laos Year under the slogan "Simply Beautiful."
Tourists come for the mountain scenery, spicy Lao food, the charms of towns like Luang Prabang and the cultural legacies of the French colonial years -- ocher buildings and nearly tax-free French wine.
But as the country opens up and embraces capitalism more vigorously, there are tensions between the old and new Laos, between a more transparent government and the more cloistered system that fought off U.S.-backed militias during what is known as the Secret War of the 1960s and 1970s.
"There's not total, 100 percent agreement or understanding about how to manage a market economy, a more globally oriented rule-of-law state and yet maintain the kind of political system they have," said Ms. Stewart, the U.S. ambassador.
The country's National Assembly has taken a more assertive role in debating government policies that were previously dictated by the top leaders. Last year, Laos completed negotiations to join the World Trade Organization and was the host of a major meeting between the European Union and the Association of Southeast Asian Nations, the grouping of 10 countries in which Laos is seeking a more active role.
At the same time, the Lao government cracked down on budding signs of free expression. In January 2012, the authorities shut down a radio program that discussed the issue of land seizures -- a hot topic with the increasing number of projects in rural areas led by Chinese and Vietnamese companies.
The host of that radio program, Ounkeo Souksavanh, said that farmers who appeared on the program were arrested several months later.
In December, the government expelled Anne-Sophie Gindroz, the head of the Lao chapter of the Swiss charity Helvetas, citing her "explicit rejection" of the Lao political system.
As for Mr. Sombath's case, the possible motives for his disappearance remain unclear. He retired last year from his organization, the Participatory Development Training Center, but continued to be engaged with nonprofit organizations in Laos.
Some speculate that going after such a high-profile personality was a warning to other private groups.
"To this day I am baffled," Mr. Sombath's wife said.
She rejects the term "activist" that many news organizations have used in describing him. "We have lived here for a long time, during periods when Laos was less open than now, when people were afraid to talk openly. We survived that period without something like this happening."
Mr. Sombath's U.S. connections may have made some old-guard officials suspicious, friends and old acquaintances say. He was an exchange student in Wisconsin in high school and went to college in Hawaii.
But his farming roots -- both his parents were rice farmers in Laos -- and his three decades of carrying out programs to help the poor won over many people. In 2005, he was awarded the prestigious Ramon Magsaysay Award, which honors public service in Asia.
Ms. Ng frets for her husband's health and safety at the couple's home overlooking the Mekong River. Mr. Sombath has a prostate condition and had been prescribed daily medication.
"I don't know where he is," she said. "I hope he is safe."
Poypiti Amatatham contributed reporting from Vientiane and Bangkok.
This article originally appeared in The New York Times.