South Korean opposition leader Kim Dae Jung, accused of plotting sedition, defied a military court today by refusing to answer many questions and declaring his trial amounted to "political repression."

Kim spoke out briefly as the first day of interrogation by military authorities began and then announced he would not respond to questions.

He sat in determined silence as a prosecutor quizzed him about his past throughout a morning session. But later in the day, after conferring with attorneys, he launched an hour-long defense of his past connections with a foreign organization that the prosecutor charged was communist-led.

Another of the 24 defendants in the trial, the Rev. Moon Ik Hwan, also spoke out, declaring that all the defendants refused to accept the trial's legitimacy. Moon and several other co-defendants were dismissed from the courtroom, leaving Kim to be tried alone.

Military authorities showed they intend to keep tight control over news accounts of the trial. A news media pool report of the proceedings was heavily edited by military censors who deleted all traces of Kim's and Moon's protests.Accounts were obtained later from observers present in the courtroom.

Kim, who for years has been this country's most prominent opposition leader, is accused of attempting to incite the overthrow of the government last spring when massive student demonstrations spread through Seoul and a violent citizens' uprising occurred in the provincial capital of Kwangju.

He could be sentenced to death or life imprisionment by the military tribunal, which is composed of four Army generals. Twenty-three alleged associates, also charged with sedition, are to be tried later.

Looking pale and rather weak, the 56-year-old opposition leader, who once nearly became South Korea's president, entered the courtroom clad in the white clothes that are a traditional Korean garb. In the 1971 presidential race, Kim won over 45 percent of the vote against the late president Park Chung Hee.

Kim told the court, according to observers, that he had no objection to the panel of the prosecutors but claimed that the trial was being used as a tool of "political repression."

He sat silent while a prosecutor began questioning him about alleged pro-communist activities as a young man. The one-sided questioning continued until a recess was finally called.

The trial pits Kim against the country's military leadership which arrested him May 17 in a sweeping crackdown on dissidents. It has governments concerned about his ability to receive a fair trial. A U.S. State Department spokesman said the charges against him seem to be "farfetched."

Families of the defendants have questioned the trial's fairness, saying in a joint statement that they had been unable to obtain legal counsel of their choice. They said 20 lawyers who normally handle civil rights cases here were taken into custody while they sought legal help, and that four others associated with the dissident movement were forced to suspend practice for one year.

The families also charged that most of the defendants had been tortured under questioning and forced to make false confessions.

Six lawyers appeared in the court-martial proceedings today apparently to act on Kim's behalf. So far, his wife has refused to agree to the court appointment of lawyers.

The trial also has international political overtones. Kim's conviction under suspect circumstances could bring down a hail of protest from other countries and affect relations between South Korea and its chief ally, the United States. Significantly, an observer from the American Embassy is sitting in on the proceedings.

The strict censorship underscores the military regime's sensitivity to the case. Two reporters for foreign media are permitted to cover each session. Their report, which was to be distributed unaltered to other reporters, was released with several passages marked for deletion.

Meanwhile, the generals who have in effect run the country under rigid controls since their May 17 crackdown proceeded to take the final steps toward placing their leader Gen. Chon Doo Hwan, in the presidency.

Sources said today that Chon will step out of uniform later this week as a necessary step toward being elected president within the next two weeks.

His election for an interim term will be formally voted on Sept. 27 or 28 by the National Conference on Unification, a 2,400-member body that acts as an electoral college. It was elected by voters in 1978 under strict control of late president Park. No opposition to Chon's election is expected.

Kim is accused of violating martial law decrees, the national security law, the anticommunist law and the foreign exchange control law.

Specifically, a lengthy indictment accuses him of financing the student uprising of last May and of attempting to instigate a violent overthrow of the elected government, with the hope of attaining power himself.

The indictment also alleges he has periodically had meetings with communists seeking to unite the country with North Korea. In the past, Kim has denied having communist associations.