CENSURED by their international patrons, Cambodia's politicians are slouching back to Phnom Penh to revive their search for peace.A compromise Tuesday defused a standoff and cleared the way for the notorious Khmer Rouge to return to the capital and live under a protective United Nations presence. The confrontation between the Phnom Penh government of Prime Minister Hun Sen and the radical Marxists was ignited last week by a mob attack on Khmer Rouge leader Khieu Samphan, who fled Phnom Penh for Thailand. For now, the violent episode is cooling the political alliance between Cambodia's recognized head of state, Prince Norodom Sihanouk, and Hun Sen, who many observers believe instigated the demonstration against Khieu Samphan. But analysts say the incident highlights deep hatreds among the rival political factions that will continue to complicate efforts to rejuvenate the war-battered country. "It's shown the Cambodians that they have to get serious about this peace process," says a Western diplomat attending a meeting of the Cambodians and their international backers in Thailand. A growing international impatience prods the Cambodian leaders to end the rivalries that had long been manipulated by major world and regional powers. Vietnam, which invaded Cambodia in 1978 to end a four-year Khmer Rouge reign of terror, installed the Phnom Penh regime and backed it during Cambodia's 13-year civil war. In a controversial alliance of three resistance groups, China and Thailand supported the Khmer Rouge while the United States and other Western countries supported the two noncommunist groups. Reduced cold war tensions and a new rapprochement between the communist governments in Vietnam and China finally prompted the signing of a UN peace accord in October. Given the touch-and-go task ahead, representatives of the five permanent members of the UN Security Council told the Cambodians that political intrigue would only endanger the process. "This is not the time for political maneuvering," says a Southeast Asian diplomat deeply involved in the Cambodian negotiations. "It creates an imbalance which could upset the delicate atmosphere needed to achieve national reconciliation." Yet, the attempted lynching of the Khmer Rouge official already is churning political alignments. Most damaged by the episode is Sihanouk, the onetime god-king who returned to Phnom Penh recently and immediately blessed a political alliance between his son, Prince Norodom Ranariddh, and Hun Sen in a move to isolate the Khmer Rouge. Sihanouk was caught off guard by the assault on Khieu Samphan and threatened to resign as head of the interim reconciliation council if new violence exploded. Stung by criticism that the political coalition had compromised his neutral stance in mediating the peace, a chastened Sihanouk backed off from plans to establish a formal coalition government with Phnom Penh officials. "We are now slowing down on the political alliance until the tension eases up a bit," said Prince Ranariddh, who analysts believe resented his father's enthusiasm for alliance with Hun Sen. For Hun Sen, who just a week ago seemed poised to turn denunciations of the Khmer Rouge to a political advantage, the Pattaya meeting became an embarrassing setback. For the Khmer Rouge, it was a diplomatic success. A Phnom Penh-based diplomat says that "people who say they hate the Khmer Rouge have started asking why the government made this provocation," jeopardizing the peace accord. The Khmer Rouge have claimed the high ground, analysts say. "They were a lot more dignified than the others," says a Western diplomat. The guerrilla group, which is blamed for the deaths of at least 1 million Cambodians during the 1970s, lost hundreds of thousands of dollars and key documents in the mob attack on its Phnom Penh residence. In addition, the group claims one of its top officials was temporarily detained and interrogated by the government and another official in charge of communications, Koh Tiang, is still missing. But by agreeing to the compromise and recommitting the group to implementing the peace plan, the Khmer Rouge showed a political shrewdness that the group could turn to its advantage. "The Khmer Rouge want to show themselves as the ones implementing the peace agreement," says Ieng Mouly, an official with a rival Cambodian faction. "They have gained some credit for that."