Lon Nol, the partially paralyzed former ruler of Cambodia, came to the lawns of his nation's deserted embassy here yesterday to ask for international support in evicting from the United Nations the current Cambodian Communist leaders, whom he described as murderers.

It was the first public foray for the 64-year-old military commander, who has been living in seclusion at a plush home in the Honolulu suburbs since the communists defeated his army in 1975. His speech was faltering, broken at times by sobs, as he made what American officials described as a hopless plea.

Barely able to hold the prepared speech in his one useful hand, Lon Nol asked "all nations, in the name of God and every group who has also been a victim of genocide - the Jews, the Armenians, the Irish and our brothers and sisters in the Third World - to help us."

Since the communist government of Democratic Kampuchea was established, an estimated 1 million people have been executed or have died of starvation because of the policies of the new regime.

Straying from his text, Lon Nol said he has not been able to sleep, since he is the man generally blamed for the communist victory. "Everyone has accused and condemned me for this," he said.

He still claims to be the only legitimate leader of the Cambodian people, a statement few U.S. officials are eager to accept. During his short visit her Lon Nol has found only one open ally in his campaign to challenge the U.N. credentials of Democratic Kampuchea and procure them for his deposed government, the Khmer Republic.

Rep. Robert K. Dornan (R-Calif.) appeared beside Lon Nol at his press conference, adding his pledge to "take steps . . . to take away the credentials of those barbarians who represent Cambodia."

Other officials found the presence of the former leader, whose side lost the war in spite of millions of dollars in U.S. aid, something of an embarrassment. Rep. Stephen J. Solarz (D-N.Y.), one of the most vocal opponents of the Cambodian communists in Congress, met with Lon Nol, but refused to be a part of his quest.

"I told him I did not want to appear indifferent to the tragedy of the Cambodian people, but there is the widespread feeling that the Khmer communists didn't win the war, his government lost it," Solarz said.

Sen. George McGovern (D-S.D.) also received a courtesy call from Lon Nol. Throughout the 15-minute meeting yesterday afternoon, McGovern only nodded as the Cambodian outlined his plans and thanked the senator for calling for military intervention against the communist regime.

Earlier this week a delegation of Lon Nol supporters visited the offices of U.S. Ambassador Andrew Young at the United Nations and were told that, despite American sympathies with the plight of the Cambodians, the United States could not sponsor an effort to take away the current regime's credentials.

Since Lon Nol overthrew Prince Norodom Sihanouk in a 1970 coup, the Cambodian seat at the United Nations has been challenged twice. In 1973 and 1974 Sihanouk, then titular leader of the communist government in exile, came close - once within two votes - to a successful challenge to the government of Lon Nol.