The top officer on the Korean desk at the State Department and American intelligence agents in Korea were convinced in the early 1970's that Tongsun Park was under the control of the Korean Central Intelligence Agency, according to information made public at a congressional hearing yesterday.

In the second day of the latest phase of hearings on U.S. - Korean relations by a House International Relations subcommittee, investigators released a summary of intelligence messages from Seoul warning American officials that Park, a businessman and socialite who had friends in Congress, was "receiving assistance from the KCIA . . . and was under the KCIA's control, but was not an 'agent' as such."

In testimony at the hearing, Donald Ranard, who headed the State Department's Korean desk from 1970 to 1974, said he, too, believed that Park "had an integral role, a very important role" in the Korean government's effort to win influence illegally among U.S. officials.

In sworn testimony this winter before Justice Department and congressional investigators, Park said he never worked for the Seoul government. He said his only contacts with Korean government officials came when he sought their help in his business as an international rice trader.

The Korean embassy here has also denied any official connection with Park.

If there is documentary evidence proving that Park worked for the KCIA, it could pose a serious problem for the Korean businessman. He has been granted immunity from prosecution on bribery and conspiracy charges against him - but only if he testifies truthfully.

Rep. Don Fraser (D. Minn), who presided at yesterday's hearing, said he had seen the secret cable traffic concerning Park and was convinced that Park had in fact worked for the South Korean government.

But Fraser demurred when asked if Park's sworn denials might constitute perjury. "It may go back to this question of how you define a relationship," Fraser said.

The definition of Park's relationship with the KCIA could have important consequences in legal cases resulting from the present investigations of the Korean influence-buying effort.

One of the charges against Park himself is that he did not register as an agent of the South Korean government here. Members of Congress who received gifts or money from Park might be charged with violating the constitutional prohibition against accepting anything of value from a foreign agent.

The summary of intelligence messages that was released yesterday was prepared jointly by the subcommittee staff and intelligence officers, Fraser said. But staff members said they were not sure about the legal impact of the summary's statement that Park "was not an 'agent' as such."

Under federal statutes, the term "agent of a foreign principal" means anyone who acts, with or without a contract, as a "public relations counsel, publicity agent, information [WORD ILLEGIBLE] employe, servant, agent, representative, or attorney for a foreign principal."

Ranard, the former State Department official, said he determined from various sources that Park "had an employment relationship of some sort with the Korean government."

In fact, documents released at the hearing showed that Ranard and his immediate superior, Winthrop Brown, who was head of the Bureau of Far Eastern Affairs, urged the U.S. ambassador in Seoul in 1971 to tell the Korean government to "recall" Park from Washington.

Ranard said he specifically used the word "recall" because of Park's employment relationship with the Seoul government. Asked what came of the proposal, Ranard said, "I don't recall."