In the two weeks since the head of Cambodia's government was ousted in a coup, the din of gunfire has given way to the usual cacophony of Phnom Penh street life, and to soothing sounds from the country's pumped-up strongman. Coup leader Hun Sen, officially still "second prime minister," has been telling the international aid donors who prop up Cambodia what they want to hear, promising to hold free elections next year, respect human rights and embrace democracy.

From Cambodia's neighbors and the West have come tones of acquiescence. The United States has publicly denounced the power grab and suspended its aid, but still refuses officially to call it a coup, in order to circumvent a potential legal bar to reinstating half the aid next month. Diplomats in Phnom Penh say the deposed "first prime minister," Prince Norodom Ranariddh, was weak and ineffectual anyway, and that Hun Sen's action has at least ended a prolonged feud that had paralyzed the government.

Behind this tepid response is a conviction that the United States and its allies can now work with the 46-year-old Hun Sen to moderate his longstanding violent, erratic and undemocratic tendencies. Ultimately, this thinking goes, Hun Sen's takeover will lead to a measure of democracy and stability for Cambodia. It is an encouraging assessment, but recent history suggests it is likely to be wrong. The United Nations has spent nearly $3 billion implementing a poorly drafted 1991 peace plan that was intended to disarm Cambodia's warring factions and produce free elections, but led instead to a rocky coalition government. The United States and other donors have coughed up another $3.5 billion trying to put Cambodia back on its feet after more than two decades of bloodshed and turmoil. All this money and effort were effectively nullified by Hun Sen's takeover on July 5 and 6.

Hun Sen's coup was hardly surprising. The seeds lay in a failure to implement the 1991 U.N. peace plan. In the six years since Hun Sen signed on to the accord, he and his generals have literally gotten away with murder, flouting the agreement's call for a government led by the victor of a free election. His political opponents have been violently repressed, without any appreciable protest from the United States or the other four major powers (France, Britain, China and Russia) that signed the accord. It is no accident that one of his nicknames in Phnom Penh is "Saddam Hun Sen." He rules by fear and enforces his decisions at the end of a gun barrel.

The diplomatic community sees Hun Sen as shrewder and more disciplined than his deposed, royalist rival, who is widely viewed as effete and inept. But the idea that Hun Sen and his minority Cambodian People's Party can hold free and fair elections by next May, as promised, borders on the absurd, according to human rights groups. One such group, Human Rights Watch-Asia, says Hun Sen's forces have executed more than 40 people in the past two weeks, including at least six top Ranariddh aides. Hundreds of royalist supporters have been arrested, six detention camps have been established for rival military officers and their families, and more than 80 opposition figures, including members of parliament, have been driven into exile or hiding.

It's a familiar pattern for Hun Sen. Although the U.N. declared the election it supervised under the peace plan "free and fair," the campaign period that preceded it was marked by a wave of terror and intimidation in which agents of Hun Sen's party killed as many as 200 opposition politicians and supporters, abducted scores of others and attacked numerous provincial party offices -- despite the presence of 20,000 U.N. peacekeeping troops from various countries. Many of the actions were explicitly discussed in official party documents that fell into U.N. hands.

Entirely focused on holding the election, pulling out of Cambodia and proclaiming the costly effort a success, the United Nations failed to implement major provisions of the peace plan, notably the disarming of the warring factions and the takeover of key ministries from the then-ruling People's Party.

"We left the four parties intact, and armed to the teeth," said Benny Widyono, the U.N. special representative who served in Cambodia from 1994 until last May. A shortage of funds made the United Nations "gamble on the election . . . as if that was the main thing about the agreement." In retrospect, he said, "we should have stayed longer in the post-conflict rebuilding process." Other former U.N. officials have criticized the operation for doing a poor job of training and equipping local police, thus allowing Hun Sen's military forces to continue to hold sway over all civilian authority.

While Hun Sen's intimidation tactics and control over the administration and patronage undoubtedly helped keep the election close, he and his People's Party fell short of their predicted victory, mustering 38 percent of the vote compared to 45 percent for Ranariddh's Funcinpec party. Still, Hun Sen refused to relinquish control, and no foreign powers protested when Ranariddh's father, King Norodom Sihanouk, pressured his son to accept a coalition government that effectively left Hun Sen in charge and, Sihanouk thought, would thus avoid a civil war.

After two years of increasing friction between Hun Sen and Ranariddh, then-secretary of State Warren Christopher went to Phnom Penh in August 1995 and saluted Cambodia's "remarkable progress . . . toward democracy and peace." A month later, Winston Lord, then an assistant secretary of state, praised "Cambodia's emerging democracy" and said the government was building the right kind of political and economic institutions. This was at a moment when military spending accounted for more than half of the country's annual budget, and judges were being paid the equivalent of about $20 a month, making corruption widespread.

The Clinton administration's posture was heavily influenced by its ambassador to the country, Kenneth Quinn, a former deputy assistant secretary of state. Quinn, who is fluent in Vietnamese and helped negotiate the U.N. peace plan, arrived in mid-1995 determined to persuade Hun Sen -- who was capable of placing U.S. citizens in the country at risk -- that Washington was not his enemy.

Quinn caused a stir by joining Hun Sen in a ceremony in Phnom Penh at which Hun Sen was awarded an honorary degree from Iowa Wesleyan University, a school in Quinn's home state. Quinn also was accused by political opposition leader Sam Rainsy of being too complacent about Hun Sen's authoritarian policies.

The State Department in its human rights report for 1996 criticized extrajudicial killings and other abuses by government security forces, but did not attribute them to Hun Sen and his party. Similarly, the Drug Enforcement Administration's status report on Cambodia in January of this year described the country as "especially vulnerable to infiltration of organized crime and money laundering," but failed to mention that some of Hun Sen's closest associates have been linked to drug smuggling by Western anti-narcotic officials.

The FBI has kept classified a report that, according to U.S. government sources, implicates Hun Sen's bodyguard unit in a March 30 grenade attack at a peaceful protest organized by Rainsy's party. An American was injured in the explosion. Hun Sen's response was to call for Rainsy's arrest and to urge the National Assembly to require that all future protests be held within a designated, fenced area with his soldiers at the gates.

Many Cambodian experts say that political considerations -- including a poll by Hun Sen's own party, showing that the party was likely to lose next year's elections -- motivated his recent power grab, rather than the claimed goal of stopping Ranariddh's from bringing Khmer Rouge guerrillas into Phom Penh. Ironically, however, the move may ultimately wind up helping the marginalized Khmer Rouge forces more than it will hurt them, handing them a propaganda windfall.

The reason is that many Cambodians still regard Hun Sen, who defected from the Khmer Rouge in 1977, as a pawn of the country's historic adversary, Vietnam. During a 10-year occupation that began when Vietnamese invasion forces drove the Khmer Rouge from power in 1979, Vietnam installed Hun Sen as foreign minister and later prime minister. Certainly, the fact that Hun Sen was visiting Vietnam when the coup began did nothing to allay fears -- xenophobic as they may be -- that Hanoi was once again pulling the strings in Cambodia. This is not to say the Khmer Rouge can make a comeback, but it is likely to have an easier time rallying opposition to the government now that Hun Sen is undisputedly in charge.

Var Huoth, Cambodia's ambassador to the United States and a close ally of Hun Sen, held a news conference here last week at which he attempted to gloss over Hun Sen's seizure of power by military force and subsequent human rights abuses. There was no coup, the ambassador said, while seated next to American public relations and legal advisers. It was merely an "appropriate military action."

The ambassador went on to explain that there have been no assassinations, just unavoidable military casualties. Reported detention camps set up to house Ranariddh loyalists are not really camps, but merely places where some of those who have violated the law or have been misinformed are being "reeducated" about what is really good in Cambodia, he said.

Of particular note was the ambassador's claim that the new government has a plan to "clean" the country of its residual opponents, in order to bring peace. It prefers to use nonviolent means, following the Buddhist tradition, but "circumstances" require the use of military force to accomplish this task, he said.

In summary, Var Huoth said that Hun Sen is delighted that the State Department "has not pronounced the word coup' " and that the new ruler of Cambodia feels his relationship with Quinn, the U.S. ambassador, remains good. There is "nothing gray or black" between the two men. Their friendship is "still very white," he said.

Indeed, the word from Phnom Penh is that the U.S. Embassy feels that the Cambodian strongman is someone the United States can deal with. But it is Hun Sen who seems to have the upper hand in these dealings. William Branigin was The Post's Southeast Asia correspondent from 1981 to 1986 and from 1990 to 1995. Jeff Smith covers national security issues for The Post. CAPTION: Cambodian government soldiers loyal to Hun Sen load captured weapons onto a van on the outskirts of Phnom Penh earlier this month.