Bangkok — After two generations at the top of Vietnam's Communist Party, Le Duan is making his first visit to a noncommunist country. He starts a five-day visit to India this Friday. Officially the visit is being described by the Vietnamese as a goodwill trip. But the real reason can probably be found in Vietnamese domestic politics: In making the trip, Le Duan, Vietnam's highest-ranking leader, seems to be signaling his personal interest in developing economic relations with the noncommunist world. He may also be signaling his support for economic policies at home that are still being contested by senior members of the Vietnamese Communist Party (VCP).
The visit is a complete surprise to outside observers and seems to have been hastily organized. Details of the trip have not yet been officially announced. What is clear is that the trip is out of character for Le Duan. His foreign travels these days are usually limited to one or two quiet trips a year to the Soviet Union.
He is a revolutionary organizer, not a diplomat. He is the only Vietnamese leader not to have a government position - obviously by his own choosing. (His only title is general secretary of the Vietnamese Communist Party.) He has been content up to now to avoid protocol, noncommunists, and journalists: He does not even give interviews to his own official newspaper. In India he will be treated to large doses of all three.
The key to the visit can probably be found in a major speech delivered to the Central Committee recently. In it, Le Duan seemed to come down on the side of the current, controversial economic policies. In doing so he called for a broadening of economic relations with the outside world, communist and non-communist alike. The trip to India may be the first sign that Vietnam wants to reach out.
The debate on economic policy has dominated Vietnamese politics for the last five years. Late in 1979, following three disastrous years for the economy, some influential party members proposed a radical change in approach. The innovations they suggested included financial incentives for farmers and most workers, as well as a degree of decentralization in planning.
After considerable resistance, the policies were gradually adopted. But they still have powerful critics - thought to include Truong Chinh, the head of state and second- or third-ranking leader in the country.
The critics feel that the policies are a form of creeping capitalism: Some of them have claimed that the reforms have tipped the scales against socialism in Vietnam.
Under these circumstances, Le Duan's apparent championing of the policies is extremely important. To the probable discomfiture of the ideological purists, Le Duan made it clear that incentives were in Vietnam to stay. People who work harder, he told the Central Committee, would receive higher wages. ''Egalitarianism,'' he continued, ''is an erroneous tendency alien to Marxism-Leninism.''
Le Duan's advocacy of increased foreign trade apparently strengthens the position of the economic reforms. They will be all the more necessary if Vietnam does succeed in broadening its commercial links with the outside world.
Although he stresses that first priority in foreign economic relations will still be given to Hanoi's communist allies in the Soviet bloc and Indochina, Le Duan also provides what looks like an ideological justification for dealing with capitalists. The two world economic systems, socialist and capitalist, he told the Central Committee, coexist and to some extent are interdependent.
Initially, Le Duan said, Vietnam should seek to increase relations with nonaligned countries. At the same time, it should attempt to do more business with the West, and break down the embargo imposed on it by ''imperialists and expansionists'' - Hanoi's jargon for the United States and China.
Le Duan's delegation reportedly includes the foreign minister and alternate member of the VCP Politburo, Nguyen Co Thach, deputy prime minister Tran Quynh, a Central Committee member in charge of foreign economic relations, and Nguyen Thi Binh, minister of education and also a Central Committee member. In addition to New Delhi, the group will visit the industrial city of Bombay.