Tongsun Park, the accused South Korean secret agent, kept a personal diary in which he described his dealings with members of Congress, including references to apparent cash payments to some of the officials.

The diary for 1972, which reportedly includes indications of payments to at least one U.S. senator whose name has not been associated with Park publicly, was impounded and sealed by a U.S. Tax Court judge last week.

Internal Revenue Service attorneys had asked for any diaries in Park's possession while preparing their case that the onetime Washington businessman owes $4.5 million in back income taxes on some $8 million he was paid from 1972-75 by Connell Rice & Sugar Co. as commissions on the sale of rice to South Korea.

Park's attorney, William G. Hundley, had argued that turning over such material "may tend to incriminate him [Park] in connection with the Justice Department's investigation of payments by Mr. Park to members of the U.S. Congress.

Park has been indicted by a federal grand jury on charges he used part of the rice commission money to bride members of Congress. Apparently neigther the Justice Department nor the House Committee on Standards of Officials Conduct, which is investigating unethical conduct by members, was aware of the existence of the diary.

Hundley declined comment yesterday on where he got the diary. He told Tax Court Judge Theodore Tannenwald Jr. at a hearing last week that the 1972 book was the only one in his possession.

Tannenwald took custody of the diary, pending a decision on whether Park's right against self-incrimination precluded turning it over to the IRS. The IRS lawyers argued in court that Park had waived that right because he had provaided the Justice Deparment with other personal documents.

The Washington Post reported las spring that Park kept personal financial ledgers which included notations indicating cash disbursements next to the names of members of Congress. But the Tax Court records are the first indication that Park also kept personal diaries.

The document might be useful to federal investigators as corroboration to other information, such as bank withdrawals and deposits, about Park's payments to members of Congress.

It might also be considered more credible than many of the reports of alleged payments which Park sent back to officials of the Korean Central Intelligence Agency. Investigators consider many of those reports exaggerated and designed mainly to impress the Seoul government, which permitted his lucrative rice commission contracts.

Park has been in Seoul, beyond the reach of U.S. authorities, since August, and the Korean government has balked so far at Justice Department attempts to get him back.

The department has agreed to drop charges against Park if he will cooperate in their investigation of the U.S. officials who toook the cash payments and testify in future trials.