KEO SOEUNG SOPHAN grapples daily with the most explosive dilemma facing postwar Cambodia: land ownership.In this decayed provincial capital along Tonle Sap lake, the veteran civil servant slowly untangles land ownership snarls left by two decades of war. But Mr. Sophan's job as provincial land tenure administrator has become formidable, even dangerous. Two years ago, the communist government in Phnom Penh began disbanding collective farms and rebuilding a formal system of private property ownership. Now, on top of other duties, Sophan must find land to resettle 4,000 refugee families expected to be repatriated from border camps in Thailand, 1,500 internally displaced families who fled fighting and attacks by Khmer Rouge guerrillas, and thousands of victims from severe flooding earlier this year. Ominously, the Khmer Rouge has seized the issue of land as a way to gain further support in rural areas. Embroiled in individual land disputes, the Marxist radicals have evicted people from contested property and attacked Sophan's village meetings. "There are great difficulties," Sophan said, seated in his office in front of a huge map of Kompong Chhnang province. "Even if I am afraid, where can I hide?" Land distribution is the linchpin of success of an ambitious peace plan for largely agricultural Cambodia. Property issues will shape the resettlement of almost 500,000 Cambodians who fled to border camps in Thailand or inside the country. Facing an unprecedented task of overseeing the refugees' return and administering Cambodia before elections, the United Nations is sending a special mission next week to investigate land use. Land ownership is among the most pressing issues for UN administrators and the interim government comprised of the four rival Cambodian factions, whose leaders already are arguing over their own personal property. "It's a tricky issue and the biggest issue that stands in the way of repatriation going smoothly," says Scott Leiper, director of the UN World Food Program. "It is not a problem just in the rural areas, but also in Phnom Penh." Equitable land distribution is crucial to Cambodia's political future, Western observers say. Already, the two-year-old land reform program has broken up more than 120,000 collectives into smaller plots. As a result, agriculture production has jumped and self-sufficiency spread among farmers. The new system of issuing deeds has begun to simplify claim conflicts and to rebuild a formal ownership system. Yet, there are also shortfalls. Without the collectives' safety net, Cambodia's most disadvantaged could be further marginalized, and the disproportionately large number of families headed by women face new difficulties. Like many aspects of Cambodian life, corruption and political influence cloud the system and can determine who gets the best pieces of land, Cambodian observers say. Still, UN officials and international aid workers say the land program is a solid step toward rebuilding institutions and checking the disarray that could be exploited by the Khmer Rouge. "What other country in the world has gone through anything like this?" asks Steve Troester, a field director with the American Friends Service Committee, a Quaker organization that is assisting the land tenure program. "This provides an overall stability so that people people know the land they are farming today will be theirs 10 years from now." A visit to the city of Kompong Chhnang underscores the enormity of the task. Buildings are ramshackle and streets overgrown and potholed. The provincial governor has resigned, leaving a political vacuum, and many civil servants have not been paid for five months. In the countryside, production is only two-thirds of that during the 1960s. Just one-sixth of irrigable land receives water. Materials to build roads and irrigation structures are often diverted to fuel Phnom Penh's building boom. While land is not a problem in Kompong Chhnang, access to good land is. Returnees who can receive up to 12 acres under Phnom Penh rules will get, in effect, far less. The southwest corner of the province is inaccessible because of Khmer Rouge control and land mines. Recently, the government discovered that an area designated for returning refugees had been mined. STILL, that has not stopped a land rush. Sophan says that 185,000 claims have been filed for the 218,000 land parcels in Kompong Chhnang province. Because of disputes, lack of access to land, and inadequate staff for surveying, only 433 formal deeds have been issued. With no functioning legal system, the official relies on a local consensus to solve disputes. But in recent months, the Khmer Rouge has begun interfering. In one instance, three families enlisted the Khmer Rouge's help to force off five other intruding families. The five families then displaced other families in what became a chain reaction affecting 20 families. Sophan recalls when he went to a village to resolve a disagreement. The Khmer Rouge attacked the outdoor meeting three times, shooting over peoples' heads and forcing them to take cover in their huts and in the forest. With no villagers available, consensus was impossible. And when Sophan supplied applications for formal land deeds to a group of internal refugees, guerrillas confiscated the forms and prevented Sophan's return. "A family may want to claim an occupied parcel and has a son in the Pol Pot group," said Sophan using the name of the notorious Khmer Rouge leader. "They can send a message [to the guerrillas] and put pressure on the landowner."