On the witness stand Chang-kun Sung seemed nervous but emphatic.

Yes, he had given an envelope containing thirty $100 bills to an official of the General Services Administration, Sung told a jury in U.S. District Court here.

But no, it was not a bribe as federal prosecutors had charged.

The money was a "Christmas present," said Sung, an immigrant from Korea. He wanted to "show appreciation" to the GSA, he said, for letting him use extra space in a downtown office building to store supplies for his small newsstand and snack bar.

The prosecution played two tape recordings in which Sung told the GSA property specialist, Emily Brinkley, that the money was a "gift" and urged her to take good care of herself. Brinkley testified that Sung had never suggested that she give the money to the government.

After deliberating five hours, the jury of 12 women acquitted Sung of the bribery charge on which he faced up to 15 years in prison and a $20,000 fine. Yesterday the jury deliberated just two hours more before finding him not guilty of the lesser charge of giving an illegal gratuity which carries a penalty of up to two years imprisonment and a $10,000 fine.

But after the jury had been dismissed, Assistant U.S. Attorney Theodore A. Shmanda told Judge Barrington Parker that instead of giving the money back to the defendant, which is usually done with evidence after an acquittal, he would make sure that Sung's "wish" was complied with by turning the money over to the U.S. Treasury.

Sung's attorney, Alan P. Bayles, did not object.

"I am grateful to the jurors," Sung, who lives in Silver Spring, said later. "I don't want to get back the money."

He added that after he left the court around noon yesterday he returned to the store and stayed, as he usually does, until about 5 p.m. Sung said he gets to work at 6 a.m. after leaving his home in Silver Spring a half hour earlier.

Sung, 44, settled in the United States in 1974 and became a citizen in 1980. He said he has operated the store since 1978 in the lobby of the Vanguard Building, 1111 20th St. NW. It is still called Judy's News after its previous owner.

About a year ago, he said he started keeping supplies in some empty space next to his store that the Labor Department was no longer using. No one ever asked him to pay rent, Sung said. But after the Labor Department vacated the building, he heard that the government would sublet the space and Sung said he wanted to lease it.

Brinkley, who was handling arrangements for the space, testified that Sung phoned her twice in December asking her to stop by to pick up a "Christmas gift." She refused both times, she said, explaining that government officials could not accept presents.

After she came by the building on Jan. 7 to show the space to somebody else, Brinkley said Sung told her he still had the gift and handed her an envelope. When she looked inside and counted the bills, she said she gave it back to him and later told her superiors and the FBI.

Three days later, with the FBI taping the call, Brinkley said she phoned Sung. After he said he still had the gift, Brinkley said she had "thought it over" and would like to accept it.

She came to the store a few hours later with a concealed tape recorder and an FBI agent nearby. This time, she said, she took the envelope and left the lobby as Sung wished her well. Agents said the FBI arrested him a few minutes later.

"Now I am very happy," Sung said after the verdict. "But I still have the problem with the space." He said GSA made him move his supplies out after his arrest.