SEOUL -- In this most staunchly anticommunist of nations, making friends with communists has suddenly become the rage.

When Transportation Minister Cha Kyu Hun unveiled plans last month to spur tourism between South Korea and such nations as China and the Soviet Union, he was only the latest to jump on a bandwagon that has been gathering surprising speed.

A day earlier, Foreign Minister Choi Kwang Soo had disclosed that the Korean trade promotion agency opened an office in Budapest in December and that Hungary will reciprocate with an office here in March. The exchange will represent the first official relationship between South Korea and any communist nation. Similar missions are expected soon from Poland, East Germany and Yugoslavia, officials said.

Officials said South Korea may even extend development loans to East European nations, despite the country's own sizable debt. Chinese language courses suddenly have become oversubscribed.

The immediate spur to the "communist boom" in a nation where books by Karl Marx still cannot legally be sold is the Olympic Games scheduled to take place here in September. China, the Soviet Union and most other Eastern Bloc nations have accepted invitations to the Games although none of them maintains official relations with South Korea -- and despite a threat from their ally, North Korea, to stage a boycott.

The longer-term goals are wider markets for South Korea's industrial goods, expanded sources of raw materials for this resource-poor nation and, perhaps most of all, increased international respectability in Seoul's 40-year-old battle to be recognized as the capital of the real Korea.

"Once the Seoul Olympics are smoothly staged, Seoul will definitely become the center of politics and culture, and Pyongyang will be degraded to the status of an illegal local government," Kim Chang Soon, director of the Institute of North Korea Studies, said in an interview.

The South Korean overtures toward the communist world are especially remarkable since they follow so closely upon the apparent sabotage of Korean Air Flight 858, which exploded in the air between Burma and Thailand last November, killing all 115 aboard.

A woman who was apprehended after flying on the first leg of that flight confessed last month to being a North Korean agent who had planted a bomb aboard the flight on orders from her superiors. Seoul harshly condemned North Korea for the attack and urged other nations to do the same.

But South Korean officials, anxious not to give other communist nations any reason to shun the Olympics, have kept the criticism focused tightly on North Korea. They also delayed publicizing the agent's confession until communist nations had responded to the Olympic invitations.

Thus, while thousands of South Koreans have staged outdoor rallies condemning Pyongyang, others have busily pursued the communist boom. Universities are scrounging for teachers and books for hitherto prohibited courses on history and society in the communist world.

The nation's government-controlled television stations are planning to exchange programs with communist nations about each other's sports training methods and daily life. The Ministry of Culture and Information is lifting a ban on musical recordings from communist nations, as long as no overtly political material is included.

Indirect trade between South Korea and the communist world has been permitted since 1972, however, and has grown markedly during the past few years. President-elect Roh Tae Woo, during his campaign last fall, promised more trade with China, partly to spur development of South Korea's impoverished west coast.

Like businessmen in many other nations, South Koreans have visions of exporting large quantities of steel, cars and other products to China's vast population. They hope to import oil, coal and other raw materials.

The trade agreement with Hungary was welcomed as an "epochal breakthrough" by the Korea Herald. A headline read, "Korea-Hungary pact paves new silk road." Officials said they may extend development loans to East European nations in the range of $50 million to $100 million this year.