PARIS, DEC. 31 -- A leading Vietnamese Communist who has surfaced here and is broadcasting calls for democratization and economic reform back to his homeland has vowed to continue his activities despite concern that he could be arrested when he returns to Vietnam within two months.

Bui Tin, deputy editor of the official Communist Party daily newspaper Nhan Dhan, arrived in Paris in September as a guest at the French Communist Party newspaper L'Humanite's annual festival. Once here, the 64-year-old party veteran began broadcasting statements back home on the British Broadcasting Corp.'s Vietnamese-language service, calling on the government to abandon Marxism and end political repression.

Tin has had a long career with the Vietnamese Communist Party. He accepted the surrender of South Vietnam in April 1975 after riding on a tank that burst through the gates of Saigon's presidential palace. Twenty-one years earlier, he was present at Dien Bien Phu, when the French were defeated by Vietnamese troops, spelling the end of French colonial rule in Indochina.

In an interview, Tin said "the time had come to speak out" for "real democratization and opening" because "the crisis in Vietnam was deepening and would only get worse in 1991." Although he acknowledged that the broadcasts angered the party leadership, he was "only saying in public what many Vietnamese party cadres and ordinary citizens long had said in private."

Despite official assurances he can return "in all security" after his extended stay in France, Tin said that he stood a "three in 10" chance of arrest for his broadcasts. His wife, daughter and son-in-law have already been interrogated in Hanoi, he said.

Bui said that upon his return he "certainly" expected to be interrogated, fired from his job and even expelled from the party.

But he said he thought his knowledge of "quite a number of state and party secrets" may protect him despite signs that his weekend BBC broadcasts are embarrassing and angering the party leadership.

The staff of his newspaper has already accused him of "distorting" party and state "policies and lines" in the BBC interviews, according to official Vietnamese radio.

Still, Tin said, he plans to continue beaming his criticism of Hanoi's political repression, rigid Marxist economics and hostility toward the United States to the BBC's Vietnamese listeners, whom he said number 2 million. The broadcasts are scheduled to end late next month.

He said "restaurants and sidewalks were nearly empty" in Hanoi on Saturday and Sunday evenings because people were at home listening to his broadcasts.

Tin's presence in France became public in late November after he issued over the BBC -- and later in the Wall Street Journal's Asian edition -- a petition to his party denouncing Vietnam's runaway inflation, mounting prices, bureaucracy, corruption and fraud in the party "entrenched in an insolent reign of privilege and prerogatives."

The petition called for the release of some 50 high-ranking party cadres, including Central Committee members, who were arrested because of their dissenting views.

He said he did not decide to publicize his dissenting views until after his arrival in France, where his visa had been extended for health reasons. He said he had suffered a major heart attack in June 1988.

Although he thought he could remain in France without difficulty, he insisted he had "no intention" of asking for refugee status.

He said he wanted to return to Hanoi by the end of February, when discussions for the party's congress, scheduled in May, is to be held at the provincial and city levels.