Former Rep. Richard T. Hanna (D-Calif.) pleaded guilty in federal court here yesterday to receiving more than $200,000 from Tongsun Park as part of a Korean government conspiracy to influence members of the U.S. Congress.

Hanna, who entered his plea before U.S. District Court Chief Judge William B. Bryant three days before he was scheduled to go on trial on 40 criminal counts, is the only former or present member of Congress so far charged in connection with the Korean influence-buying scandal.

The Justuice Department filed a lengthy "offer of proof" with Hanna's plea that said he conducted various activities on behalf of South Korea in return for the money, including inserting pro-Korean statement in the Congressional Record, initiating good-will trips to Korea by congressional delegations, and even recommending to Korean President Park Chung Hee at one point that businessman Tongsun Park be appointed as a press agent for Korea.

"The government does not have any evidence to indicate that Hanna transmitted or aided anyone else to transmit any currency or checks to any other United States congressman," Justice Department attorney Jeffrey S. White said in a letter to Hanna's attorney that spelled out the plea-bargaining agreement that resulted in Hanna's action.

Hanna could be sentenced to a maximum prison term of five years and fined up to $10,000, or both, and White said in the letter that the government reserved the right to ask for the maximum term. The plea agreement specifies that Hanna must testify truthfully for the government in the continuing Korean investigation.

Justice Department officials obviously were sensitive to how the plea-bargaining arrangement might be construed. They emphasized yesterday that with with Hanna's plea to a single count they hadn't "given up" anything because prison terms longer than five years are seldom handed down in white-collar cases.

They also cautioned that while Hanna will be available now as a government witness in other cases, his self to any new prosecutions. His cotestimony is not likely to lead by itrorboration might be be helpful in the "handful" of cases Justice still expects from the two-year Korean influence buying investigation officials said.

The negotiations between Justice and Hanna's attorney, Charles McNelis, were initiated earlier this week by McNeils, with the final plea agreement letter being signed by Hanna early yesterday morning before the courtroom appearance, a Justice official said.

Hanna, who left Congress in 1975 after 12 years in office sat impassively, hands folded as White read a 33-page summary of the proof the government would have offered at trail.

After the long recitation, Hanna tried to explain his involvement with Park. "I have a simple exposition of what happened and where I have been wrong," he said, but Bryant cut him off.

Hanna refused later to talk with reporters. His attorneys said he will reserve public comment until afetr his sentencing. No date for that has been set.

The prosecution's summary of the trial proof and the accompanying exhibits makes several points - some new, some only stronger evidence of previous government assertions.

Among them:

Hanna's many letters to Korean government officials - successive heads of the Korean Central Intelligence Agency as well as President Park - show that he was in effect a Korean agent himself. The letters would have been the basis for government's case.

Several sitting members of Congress, including House majority whip John Brademas (D-Ind.) and former whip John J. McFall (D-Calif.) would have been called to testify about letters they also wrote to Korean officials.

Hanna often "inflated" and "fabricated" some claims of contacts with other members, the summary noted.

Brademas and McFall, and other current members mentioned in the case summary, have acknowledged receiving cash from Tongsun Park. And while none apparently is facing criminal investigation, a parallel investigation by the House Committe on Standards of Official Conduct has been studying such actions for possible ethical violations.

A committee investigator said yesterday that Hanna's plea will clear the way for public testimony by Tongsun Park starting April 3.

A footnote in the summary of proof referring to former Korean ambassador Kim Dong Jo is likely to elate the House committee and frustrate the State Department.

It says one Hanna letter refers to "a rivalry between Park Ambassador Kim Dong Jo as to whether Park or Kim should direct the Korean lobbying activities Congress."

The House committee has been demanding that the Korean governent make Kim, now a close adviser to President Park, available for questioning about alleged payments he made to members of COngress. The State Department has supported Korea's contention that doing so would violate international rules of diplomatic immunity.