The South Korean ambassador to The United States from 1967 to 1973 personally prepared envelopes stuffed with cash for members of Congress, and at least one time personally delivered the cash to a congressman, according to testimony yesterday on the Korean influence-buying scandal.

In the first public presentation of its 10-month investigation of the Korean case, the House Committee on Standards of Official Conduct heard witnesses testify that the former ambassador, Kim Dong Jo, was personally involved in in the effort to buy congressional friends for South Korea.

The witnesses, including two former officials of the Korean embassy here, also linked South Korean President Park Chung Hee, President Park's late wife, and officials of the Korean Central Intelligence Agency to the activities of two Washington businessmen who have been indicted for conspiracy to bribe congressmen.

In opening statements yesterday, the committee chairman, John J. Flynt Jr. (D-Ga.), and its special counsel, Leon Jaworski, both indicated that the next two days of testimony will provide further evidence that the South Korean government was responsible for, in Jaworski's phrase, "a plan to buy off American congressmen."

The Seoul government has denied any link to the influence-buying effort. Strong proof of a government connection could be costly to South Korea, because it might lead Congress to cut back American aid to the nation.

Kim Su Doc, information officer at the Korean Embassy, said yesterday he would not comment on the hearings until they are completed.

Jaworski and Flynt both made it clear yeaterday that they expect the revelations from their hearings to increase the pressure on Seoul to co-operate with U.S. investigations of the influence-buying scandal. Jaworski recommended a House resolution demanding full South Korean cooperation.

Jaworski complained again that, without such cooperation, his investigation into wrong doing by individual members of Congress will be badly hampered. For that reason, he said, the committee is not yet ready for hearings on alleged misdeeds by members.

Under groung rules agreed to by the committee members, there was no mention yesterday of members of Congress who received the cash allegedly distributed by Kim Dong Jo, the former ambassador. When a witness talked about Kim's visiting a congressman's office, the congressman was not identified and no committee members asked whose it was.

The most direct testimony implicating the former ambassador at yesterday's hearing came from Jai Hyon Lee, a former information officer in the embassy here who subsequently broke with the Park Chung Hee government and took asylum in the United States.

Lee recounted a meeting he attended in Seoul in 1973 in which he was informed of a KCIA plan "to seduce and buy off - that's about the closest I can translate the Korean - the Congress."

Lee also told of a series of meetings at the Korean Embassy here in which KCIA officials explained the influence-buying scheme to agency officials and ordered strict security precautions for it.

Lee described a day in the spring of 1972 when he walked into the office of Ambassador Kim Dong Jo and saw him busily stuffing $100 bills into plain white envelopes. Lee said he saw about two dozen stuffed envelopes on the ambassador's desk.

According to Lee, the ambassador said "I have to deliver these things."

"I asked him where he was going to deliver them," Lee testified. "He said, 'To the Capitol'."

Lee did not say that he ever saw Ambassador Kim deliver money to a congressman. That part of the story was filled in by another witness, Nan Elder, personal secretary to Rep. Larry Winn Jr. (R-Kan.).

Elder told the committee that "a gentleman from the Korean embassy" visited Winn's office in September, 1972, a day or two after Winn had attended a Korean Embassy reception. She said the visitor left an envelope in Winn's office, but that the congressman rushed off to a committee meeting without opening it.

Elder said she opened the envelope, and found an inch-thick stack of $100 bills. She contacted Winn, she said, who told her to find the Korean visitor and give the money back.

Accordingly, Elder called the embassy to ask where she might find the mysterious visitor. She was told to call the office of another congressman, and she reached the Korean there. He returned to Winn's office and took back the money, Elder said.

Elder said the Korean visitor was a stranger to her.But she identified a photograph of him that was provided by committee investigators. Jai Hyoon subsequently identified the photograph as one of Ambassador Kim.

Elder did not name the other congressman in whose office she reached the Korean ambassador. The committee members did not ask the congressman's name.

Lee and another witness, Kim Sang Keun, a former KCIA official who broke with the Seoul regime in 1976, linked korean President Park Chung Hee and his late wife to the activities of two Washington businessman, Tongsun Park and Hancho Kim, who have been indicted in the influence-buying investigation.

Lee said that in 1971 or 1972 Ambassador Kim showed him a handwritten letter from President Park saying "don't quarrel with Tongsun Park. Give him good cooperation."

Kim Sang Keun was the only witness at yesterday's hearing who has not told his story in public before. He has been under protective custody since he broke with the Korean government last November, and has assisted Justice Department investigators with their probe of the Korean case.

Kim Sang Keun, who said he served as a KCIA agent in the Korean embassy here, offered considerable detail about the operations of Hancho Kim, a Washington businessman who allegedly was to distribute money to congressmen as part of a Korean program code-named "Operation White Snow."

Kim Sang Keun said Hancho Kim told him that Mrs. Park Chung Hee had personally asked him to "contribute effort" to the South Korean cause.

The "contribution as Kim Sang Keun described it, called for Hancho Kim to use $600,000 provided him by the KCIA to entertain and gain influence with members of Congress.

To assure secrecy for "Operation White Snow," all participants were given code names, according to the testimony. Hancho Kim was to be "Dr. Hamilton," the KCIA official directing the plan was called "Catholoc Father," and president Park was "the patriarch."

The reason for the Korean effort to win friends in Congress, Lee told the committee, was that "Park [Chung Hee] was very worried about losing U.S. support - military and economic support - without which the government could not stay in power."

Yesterday's hearing had all the paraphernalia of a major congressional investigation. The room was jammed with cameras and klieg lights, and reporters filled three long tables across the front of the room.

But much of the tension dissipated as the afternoon wore on. For personal protection, Kim Sang Keun demanded that all cameras be turned off when he testified. He answered questions through an interpreter, and made painfully slow progress that had audience and committee members alike restless and yawning.

The hearings are to begin again at 11 a.m. today. WETA-TV (Channel 26) is televising the hearings in the Washington area, but will not be permitted to broadcast until Kim Sang Keun's testimony is finished.