Le Duc Tho, 78, chief communist negotiator of the cease-fire talks that ended U.S. combat involvement in the Vietnam War and winner of the 1973 Nobel Peace Prize, died yesterday at an army hospital in Hanoi. He had cancer.

Tho was a lifelong communist and revolutionary. He participated in strikes and riots while still in his teens, was a founding member of the Communist Party of Indochina and was imprisoned by the French colonial government. He later served in an underground movement in South Vietnam to work for communist unification of his country.

He rose to membership in the party Politburo and the secretariat of the party Central Committee. He also became the party's expert on organization and ideology. In 1968, when the United States and North Vietnam opened peace talks, observers ranked Tho between third and fifth in the party hierarchy.

He went to Paris as a "special adviser" to the North Vietnamese delegation. It quickly became apparent that the "adviser," the only member of the delegation who could make hard decisions on his own authority, was its leader.

The peace talks soon bogged down in an exchange of vituperative charges and demands. On Aug. 4, 1969, Tho secretly met with National Security Adviser Henry Kissinger.

In secret meetings that continued in 1970 and 1971, Kissinger found Tho, as he later told a reporter, "tough, secretive, sometimes exacerbating -- difficult to come to terms with." At the same time, the two built what observers later believed was a mutual regard. As a result, the two, again in Kissinger's words, crossed negotiating "mountains and ravines."

Although his negotiating opponents called Tho "inchworm" and "doctrinaire," they also hailed the silver-haired, plainly dressed envoy's courtesy and intelligence.

The Paris accords were signed in January 1973, resulting in the withdrawal of U.S. combat forces from Vietnam, an exchange of prisoners and a cease-fire. In October, Tho and Kissinger won one of the more controversial Nobel Prizes in history.

Although the head of the Nobel committee hailed Tho and Kissinger for successfully concluding three years of difficult talks that "brought a wave of joy and hope for peace over the entire world," two of the five members of the Nobel Peace Prize committee offered their resignations in protest.

In the verbal firestorm that followed, critics on the political left protested that Kissinger was the leading representative of the country and government that had kept military intervention going for so long. Critics on the right called Tho the personification of a totalitarian state that had been at war with others, and crushed its citizens, for more than 40 years. Others said that both men, however honorable and skilled, were more closely identified with war than peace.

Tho declined the prize, stating that it was not possible for him to accept it while fighting continued in Vietnam. The war ended by 1975 with all of Vietnam under communist rule.

Tho, like most revolutionaires of his time, not only lived a secretive life but had a past shrouded in contradiction and mystery. He was born in the village of Dich Le in Nam Ha province, in what became North Vietnam. Although his official party biography claims he was the son of peasants, other sources say his father was a middle-ranking civil service official in the French colonial administration.

Tho worked as a radiotelegrapher for the post office while organizing demonstrations against the French administration. Soon after helping Ho Chi Minh, the future leader of North Vietnam, found the Communist Party of Indochina in 1930, he was sentenced to 10 years in prison.

Fellow prisoners are said to have nicknamed him "Tho the Pon Phonograph." He had the impressive, if not entertaining, ability to recite seemingly endless pages of memorized Marxist-Leninist text for his literally captive audience. After his release in 1936, he began working as a communist propaganda official.

He was imprisoned again before World War II, some claiming he escaped in 1940 to China, where he helped Ho found the Viet Minh in 1941. In 1945, he was elected to the Central Committee and the standing committee of the Communist Party.

In 1948, he was sent to South Vietnam, where he eventually became leader of the communist movement. In 1955, the year after France withdrew from Vietnam, Tho returned to Hanoi, the Politburo and other high posts. In 1956, he represented Vietnam at a Soviet party conference. In 1960, he won election to the secretariat of the Central Committee.

It is generally agreed that Tho took over a large degree of the political direction for the struggle for South Vietnam, pushing a hard line favoring unwavering combat to unify the country. By 1967, North Vietnamese documents identified him as "chairman for the supervision of the south." He also is said to have supervised party purges of opponents.

As an organizer and theoretician of the communist triumph, he remained on the Politburo, where it was believed he helped mastermind the 1978 invasion of Cambodia, until he was removed by reformists in 1978. While still believed to be influential with the party's older and more conservative elements, he seemed to have lost power among the younger guard. At the time of his death, he was "adviser" to the party's Central Committee.

IDA E. SEATON

Postal Clerk and Volunteer

Ida E. Seaton, 80, a former teacher and retired Postal clerk who was active in church and volunteer groups, died Oct. 11 at her home in Glenn Dale. She had a heart ailment.

Mrs. Seaton was born in Bowie and graduated from Upper Marlboro High School. She was a 1929 graduate of what was then the Maryland State Normal School in Towson.

From 1929 to 1932, she taught school at Brentwood Elementary School in Prince George's County and Fairland Elementary School in Montgomery County. She worked at the Glenn Dale Post Office from 1946 until retiring in 1969.

Mrs. Seaton had been a member of Glenn Dale Methodist Church since 1947. She had served on the church board and the Women's Society of Christian service. She also had been a Sunday school teacher and had served as children's division superintendent for more than 20 years.

She was a past president of the Glenn Dale Elementary School PTA, a past treasurer of the Glenn Dale Citizens Association and a charter member of the ladies auxiliary of the Glenn Dale Fire Association. She had been a member of the women's auxiliary rescue squad in Glenn Dale during World War II.

Mrs. Seaton was a 1986 recipient of an outstanding senior citizens award from the Maryland Jaycees.

Survivors include her husband, Gerald A. Seaton Sr., and a son, Gerald Jr., both of Glenn Dale; two daughters, Shirley S. Brumbaugh of Seabrook, Md., and Sonia S. Metelsky of Bethesda; a brother, Ira S. Phelps of Bowie; 10 grandchildren; and eight great-grandchildren.