THE Nov. 14 arrival of Prince Sihanouk marked another important step in turning the Cambodia peace accord into reality. But unless the five permanent members of the United Nations Security Council (the Permanent Five) and the UN as a whole actively and continuously manage events, the accord will unravel.In Cambodia, expectations are tempered by reality; the accord is greeted with hope and a heavy dose of apprehension. Families await husbands and fathers with joy, but a definitive peace agreement, which seems to be the expectation abroad, is seen here as far less certain. For starters, consider the Khmer Rouge. There is a lot of wishful thinking about the "changed" Khmer Rouge: KR genocide is not even mentioned in the peace treaty. Indeed, the KR have put a clean face forward, which contrasts with the sometimes wild and woolly corruption of other factions. But do not be fooled. Several weeks ago at the Site 8 camp along the Thai-Cambodian border the KR showed that they are quite prepared to revert to their old method of ruling by terror. At Site 8, 44,000 civilians face forced return to KR zones of Cambodia. Unless the UN and the Permanent Five can induce the Thai government to exert restraint on the KR, the principle of free choice for Cambodians on the border - a central tenet of the accord - will be violated, thus calling into question the entire agreem ent. The KR is trying to insure that it maintains the maximum electoral turn-out in the UN-conducted voting for a new Cambodian government. But this election may be almost two years off, during which time all factions will be attempting to promote their vote. The election provision may prove to be an ill-advised Western transplant, which promotes instability. Even in established democracies, election campaigns often produce turbulence. The Permanent Five should consider the possibility of advancing the Cambod ia electoral timetable. Already, inside Cambodia the KR are said to be threatening farmers with loss of land if they vote the wrong way. Some rural Cambodians say that the KR are kidnapping family members who will be held hostage to insure a "correct" vote in the election. APPREHENSION in Cambodia about the KR grows. In Phnom Penh, many believe the KR will insist that the Tuol Sleng memorial depicting KR torture be closed. The KR will have representation in the city after the accord is signed. Many Cambodians can't understand how Pol Pot can have a presence in their capital again. And make no mistake about it, Pol Pot is still calling the shots for the KR. Will the UN observers be sufficiently numerous and effective to monitor the KR, and will the Permanent Five show the will necessary to deal with them? Beyond the Khmer Rouge, the UN has another important task: de-mining. The road to the new world order is paved with both good intentions and land mines. The UN has apparently not yet centralized responsibility for leading mine removal, which is needed in places ranging from Somalia to Afghanistan to Cambodia. Governments able to provide equipment and expertise want a serious, comprehensive UN lead. The secretary-general should establish a de-mining framework without delay, perhaps through the UN peacekee ping office. Another major challenge for the UN is law and order. As the Cambodian military factions demobilize their soldiers, lawlessness and violence may increase. The UN must be prepared to maintain civil order during Cambodia's transition, possibly through a special police force. Ex-soldiers might be deployed on public works projects, rebuilding Cambodia's infrastructure. Right now, Phnom Penh and many provincial capitals are bustling with economic activity. Houses are being spruced up, market goods proliferate, and traffic grows daily. Already Phnom Penh has more traffic than in the pre-war Sihanouk era. The nouveau-riche traders do not represent widespread gain. Profit typically derives from illegal timber cutting and other exploitation - often fanned by businessmen from Japan, Singapore, and elsewhere - with profound long-term negative effects. Corruption abounds. Some how ways must be found to reduce the bribery and to protect the environment. Upgrading road and rail transport and telecommunications should have a high priority, both to redevelop the country and to prevent the KR from spreading. Fruit plantations in the Battambang area, for example, are now being cut off by KR armed personnel. Improving communications and economic activity should open up the country and make it more difficult for the KR to undermine the society. Let us hope that the international community stays with Cambodia for the long run. The world now has a second chance to deal with the KR, but that means keeping a vigilant and effective watch.