A U.S. Information Agency employe and a Vietnamese economist here were charged yesterday with funneling classified diplomatic documents to the Hanoi government through an international espionage network that allegedly involved Hanoi's ambassdor to the United Nations.

An indictment voted by a U.S. grand jury in Alexandria and made public yesterday by the Justice Department charged Ronald Louis Humphrey, of Arlington, with stealing cables sent by overseas American diplomats to the USIA communications center where Humphrey worked.

Humphrey gave the cables, according to the indiciment, to David Truong, known as Truong Dinh Hung before he entered the United States in 1965 to study economics. Truong is the son of a Vietnamese peace candidate who came in second to Nguyen Van Thieu in the 1967 election and was subsequently imprisoned for five years.

Thruong is accused of turning the documents over to couries at clandestine meetings in locations like the Landmark Shopping. Center in Alexandria for delivery to Hanoi officials stationed in Paris. Humphrey's job in the USIA gave him access to sensitive diplomatic cabies between American embassies overseas and the U.S. State Department that came into the USIA for evaluation.

The materials, basically letters home from the nation's highest ranking representatives in Southeast Asian countries, provided detailed sightsinto the American view on a wide range of political and military activities, according to persons familiar with the cable traffic.

Documents listed in the indictments, most of which were dated in the Spring of 1977, included the views of the American consul in Hong Kong on Sino-Vietnamese relations, a report from the American embassy in Thailand on a coup attempt there, and a report from the American embassy in Laos on the arrival of Russian advisers there.

Some documents seemed more innocuous, including, for example, a message from the American Embassy in Thailand to the Secretary of State about "French Flights from Saigon," information about which Hanoi government would surely already be aware.

The ultimate recipient of material allegedly was, in most cases, the Hanoi delegation in Paris, where talks are being held concerning the normalization of relations between the U.S. and the Socialist Republic of Vietnam, according to the charges and investigators. The last round of talks were held in December.

Many of the pilfered documents could give Hanoi negotiators clues and behind-the-scenes information on positions being taken by American officials at the negotiating table, according to government sources.

The two men are being held in Alexandria jail in lieu of $250,000 bond after being charged in the seven-count indictment with espionage, theft of government documents, failure to register as foreign agents, and related crimes.

Humphrey, 42, is employed at USIA as a $30,000-a-year evaluations officer in the plans and programs section. He lives at 618 S Irving St., Arlington. At a court appearance before a U.S. judge in Alexandria yesterday, a prosecutor, uring that Humphrey be held without bond, said the suspect "had access up to the time he was arrested this morning" to sensitive classified documents being monitored by the USIA.

Humphrey is the first employe of the USIA ever charged with espionage, agency officials said.

Some of them first learned of the charges against Humphrey when news of his arrest flashed over wire service teletype machines in the USIA communications room from which Humphrey was alleged to have taken the cables. Humphrey was arrested at about noon at the USIA building at 18th street and Pennsylvania Avenue NW.

Truong, 32, of 2000 F St. NW had been a well-known antiwar advocate here who contributed to number of magazines and newspapers.

Associates of Truong said he lobbied intensely on Capitol Hill and elsewhere. He was arrested yesterday at the Animal Health Institute, where he was employed as a mailroom manager while stydying for a graduate degree in economics at George Washington University.

The Hanoi ambassador to the United Nations, Dinh Ba Thi, was named as an unindicted coconspirator. Justic Department officials say Thi is immune from prosecution because he is a foreign diplomat.A State Department official said late yesterday that the U.S. was taking the matter up with the U.N. Secretary General. This is a apparent indication that the U.S. may ask that the ambassador be ejected from the the country.

Also unindicted, but named as aprticipants in the spy scheme, were Huynh Trung Dong, and official of the Association of Vietnamese in France described by U.S. sources as a "front group" for the Hanoi government; Nguyen An Huynh, head of the Department of Science and Technology, a government agency in Hanoi; Nguyen Ngoc giao, an Association of Vietnamese official in Paris, and Phan Thanh Nam, an official in the Hanoi embassy in Paris.

The indictment officially charges Truong and Humphrey with knowingly and willfully giving the Hanoi government "documents, writings, notes, and information relating to the national defense of the United States."

Persons familiar with the investigation said the documents listed in the indictment were among "dozens" that supposedly were handled by the two men during the conspiracy, which the Justice Department says began in 1976 and continued through yesterday.

While the descriptions of the documents in the indictment revealed little about their actual contents, investigators said the docoments concerned sensitive diplomatic matters and their premature disclosure to the Hanoi government could have "potentially severe" results on the national security.

Information in the documents included material concerning "United States political, military, and diplomatic relations, efforts and intelligence assessments in Thailand, Singapore, the SRV (Hanoi), the Peoples Republic of China, and Ethiopia," the indictment said.

In addition, the indictment charged that Truong and Humphrey used fictitious names, codes, fake addresses and other means to hide their alleged spy activities.

The indictment outlined instances in which Truong would deliver documents to couriers in locations in Virginai and Washington for delivery to Hanoi officials in France, and says the two men met once at Humphrey's Arlington home.

The indictment also charges that Truong visited the Hanoi mission to the U.N. in December, 1977.

After their arrest yesterday in Washington, the two men were questioned by FBI agents and transported to U.S. court in Alexandria.

At a hearing before U.S. District Judge Albert V. Bryan Fr., prosecutors said the government has a witness who is prepared to testify that he had received national security documents from Humphrey so they could be transported to the Vietnamese government in Paris.

Prosecutor Duham said bond should not be set for Humphrey or Truong in any amount because of the likelihood of their fleeing the jurisdiction. "It is highly unlikely that we would ever see Mr. Truong again if any bond made by this court could be made by his government," Dunham said, arguing that Truong was a Vietnamese agent who might still have sensitive information in his head that he could transmit to the Hanoi government.

Truong was represented in the court proceeding by Marvin Miller, an attorney who told reporters afterward that "I've talked to my client only briefly to establish he's lived here a number of years, that he's not been involved in any criminal activity and that we intend to plead not guilty.

Each man could be sentenced to a maximum of life imprisonment upon conviction of the espionage charges.

Justice Department officials said the FBI had been investigating the alleged spy network for two years and that the investigation was continuing. They refused to comment on the motive for the alleged spy activity on the part of either individual.

In a statement announcing the indictment, the Justice Department said that "once it became known that State Department documents were involved, the Department of Justice worked closely with the Department of State and the USIA to protect the confidentiality of Department of State processes and documents during the course of the investigation."