A federal judge here yesterday dismissed the government's contempt of Congress indictment against already convicted Korean-born businessman Hancho C. Kim.

In doing so, U.S. District Court Judge John Lewis Smith Jr. noted "the unique fact" that the contempt charge was based on Kim's refusal to answer the same question for which he'd already been convicted of perjury.

That questioning, by investigators for the House Committee on Standards of Official Conduct, came only four days before he was to be sentenced on the perjury conviction in May of 1978. Thus, Smith ruled, the committee's grant of immunity was "insufficient protection against use of his answer in the pending criminal proceeding . . ."

In his brief arguing that the contempt charge should be dismissed, Kim's attorney, David Povich, quoted House investigators as threatening to tell the sentencing judge that Kim refused to answer.

"In this way the special staff hoped to influence the sentencing . . .," the brief said. "Apparently dissatisfied with Mr. Kim's cooperation [they] hoped to ensure that Mr. Kim received a stiff sentence."

Kim had been convicted the month before of lying to a grand jury when he denied receiving $600,000 from Korean CIA agent Kim Sang Keun.

After not touching that area in four previous rounds of questioning Kim the previous November, the House investigators called him back for a single question: "Did there come a time when you received some money from Kim Sang Keun?"

On the advice of his attorneys, Hancho Kim, a naturalized American citizen, refused to answer. He cited his Fifth Amendment right against self-incrimination.

Though Kim was convited of conspiracy and perjury in the investigation of South Korean influence-buying in Congress, the government produced no evidence that he bribed members of Congress.

Instead, his trial showed that he used the money, which came in two $300,000 cash installments, to pay off debts and make lavish purchases of furniture and cars.

With the dismissal of the Kim case yesterday, only one indictment remains from the Justice Department's 2 1/2-year-long investigation. Former representative Nick Galifianakis (D-N.C.) is facing trial on perjury charges after denying that he accepted $10,000 in cash from another Korean businessman, Tongsun Park, in 1972.