South Korean President Chun Doo Hwan restored this morning the political rights of 84 persons who have been forcibly banned from politics for the past four years.

But Chun let stand bans against 15 other persons, including three men considered to be the most important figures in the opposition, Kim Young Sam, Kim Dae Jung and Kim Chong Pil.

The move appears to be the last significant liberalization measure that Chun will implement before National Assembly elections expected in February.

A government statement issued today said that the 84 had contributed to corruption and unrest in the past but now were "remarkably repented and reformed."

Among those regaining their rights are Lee Chul Seung, former president of the disbanded opposition New Democratic Party, and Kim Dong Young, a close associate of Kim Young Sam.

There is talk in Seoul that members of the group may form a new party for the election. But some opposition figures are arguing for boycotting the vote.

Chun, a former Army general, imposed harsh controls on politics and freedom of expression after he took power in 1980 following the assassination of president Park Chung Hee. He has relaxed them in stages since then. But, citing a threat from Communist North Korea, the government continues to hold an authoritarian grip on many political events here.

With the Soviet Bloc already hinting at boycotting the 1988 Olympic Games, which are to be held in Seoul, Chun is believed to be anxious to cultivate an image of statesmanship and moderation abroad. However, he has not given up the political ban as a weapon. Banned people cannot vote, run for office, hold party posts, give speeches or take part in politics in any way.

In 1980, 835 persons were banned. By February this year, all but 99 had had their rights restored.

In an interview at his home in Seoul two days ago, Kim Young Sam, former head of the New Democratic Party, said Chun's government is "trying to give the impression that things are moving ahead." But he said political freedom remains severely restricted and Chun's government very unstable. "The fact that they don't feel able to restore the rights of all 99 is a clear indication of their lack of self-confidence," he said.

Despite the ban, Kim Young Sam has cofounded a group called the Council for Promotion of Democracy and meets with students and other opposition figures.

Kim Dae Jung, the New Democratic Party's candidate for president in 1971, has been in the United States since he was released from prison in 1982. He recently announced plans to return to Korea.

Kim Chong Pil, the last of the opposition's "Three Kims," headed Park's ruling party. After Park's death, he was considered a possible presidential candidate.