The South Korean government has assured House leaders that former ambassador Kim Dong Jo will supply investigators with details about cash payments he is alleged to have made to members of Congress.

Rep. John J. Flynt Jr. (D-Ga.), chairman of the House Committee on Standards of Official Conduct, announced the agreement yesterday, saying it marked a breakthrough in an investigation that has been stymied without Kim's testimony.

The former ambassador is suspected of having made or directed payments to as many as 10 current members of Congress while serving in Washington in the early 1970s.He is considered as valuable a witness as the more widely known Tongsun Park.

Committee sources declined to spell out the specifics of the arrangement for the written questioning of Kim. But there was no indication that his answers would be given under oath or that he would be subject to cross-examintion, seemingly vital requirements for using any of his information for disciplinary proceedings.

Just last week the Korean government had rebuffed what appeared to a final appeal by House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) to allow two committee members to meet personally in Seoul with President Park Chung Hee to discuss ways of getting Kim's testimony.

The reversal came the day after Leon Jaworski stepped aside as active special counsel to the committee. Sources said Jaworski's action was necessary step for the Koreans' cooperation because he is viewed in Seoul as an enemy who has badgered and threatened the Park regime.

"Leon's the most hated man in Korea next to Kim II Sung [the communist dictator of North Korea]," one source said.

John W. Nields Jr., the committee's chief investigator, said the written questions for Kim will be trasmitted to the Korean government in a few weeks.

Flynt said in his announcement the Koreans had assured Congress that Kim would supply "new and concrete factual information regarding his fi-[TEXT OMITTED FROM SOURCE]

In his only public statement on the issue, Kim told Newsweek magazine several months ago that he had never given cash to members of Congress. Jaworski had held out for getting Kim's testimony under oath, saying anything less would amount to another Newseek interview.

But Nields said yesterday that the committee had promises Kim would provide some affirmative responses to the questions. "If we get a series of 'nos' we will have been misled," he said. "The Koreans know that would be a very very dangerous thing to do."

Public hearings last fall produced testimony that Kim was once seen taking about two dozen cash-filled envelopes to Capitol Hill, and that he or his wife tried to make cash payments to three House members in Washington or Seoul.

Kim's evidence is considered especially important because he was a known Korean official. It is a violation of the U.S. Constitution for members of Congress to accept gifts from foreign dignitaries.

Members who accepted cash from Washington businessman Tongsus Park - an accused operative of the Korean Central Intelligence Agency - have claimed they had not way of knowing Park was working for the Korean government.

The usefulness of any evidence Kim provides is questionable without arrangements to allow accused members to cross-examine the former ambassador.

Justice Department officials, said yesterday that written answers from Kim would be helpful to them by providing investigative leads. "But we need a live witness in court," one knowledgeable official said.

The Koreans and the U.S. State Department have argued that Kim was protected from testifying by his diplomatic immunity.

The former ambassador resigned from his position as a foreign policy adviser to President Park after the House voted to cut off $56 million in economic aid to protest Korean intransigence. But the Koreans remained adamant until now about allowing him to be questioned in any form.