A former executive assistant and chief of marketing for the D.C. lottery board pleaded guilty yesterday in federal court here to accepting $5,500 in payoffs and the use of a Honda car from a lottery board contractor.

The plea by Alexander Exum, 53, is the first conviction stemming from a 2 1/2-year FBI investigation of the way the board awarded contracts in the city's multimillion-dollar legalized gambling operations.

U.S. Attorney Joseph E. diGenova, who is directing a series of corruption investigations of D.C. government officials, said of the lottery board probe, "We expect further indictments . . . . There will be more."

Assistant U.S. Attorney David Eisenberg said in court that Exum and another person conspired in 1984 to seek $50,000 from Han Yong Cho, owner of Washington Cash & Carry, a wholesale food distribution company, in exchange for Cho's receiving contracts to store printed lottery tickets and to lease office space to the Lottery Board.

Eisenberg declined to identify the other participant in the scheme, who has not been charged. Cho, who no longer has any lottery contracts, has been granted immunity for cooperating with the government and has not been charged.

In another ongoing probe, Ivanhoe Donaldson, a former deputy mayor and top political aide to Mayor Marion Barry, testified yesterday for about two hours before a federal grand jury investigating the role of three former top D.C. Department of Employment Services officials, including former department director Matthew F. Shannon and deputy director James George.

Donaldson is serving a seven-year prison sentence for defrauding the District government of about $190,000, much of which came from Employment Services.

Exum pleaded guilty to two felony counts -- one count of conspiracy to accept an illegal gratuity and one count of tax evasion for paying no federal income taxes for 1984 -- the year when he received most of the payoffs. He also pleaded guilty to two misdemeanor counts of theft for receiving unemployment benefits while he was working full time for the District government.

Exum's plea followed several months of negotiations between Exum, his lawyer, David Woll and Eisenberg. At the government's request, U.S. District Judge Norma Holloway Johnson sealed the agreement under which the government will not bring additional charges against Exum in exchange for his cooperation.

Exum, who now lives with his mother in Hampton, Va., resigned his $45,000-a-year lottery board job in November 1984 after it was disclosed that his wife was using the Honda. He gave only brief answers to Johnson's questions during the hour-long proceeding and later declined to comment.

Exum was released on personal recognizance and sentencing was set for May 30. He faces up to 12 years in prison and $112,000 in fines.

Eisenberg gave the court the following account of the payments:

The scheme began in mid-January 1984 when Exum, who was visiting prospective sites for storing lottery tickets, went to Cho's business in the Florida Avenue wholesale food market area and ran into the unidentified man. After talking to Exum, the man told Cho that he would have a better chance of getting the contracts if he paid $30,000 to a lottery board official.

Cho told the man that $30,000 was too high, but that he was willing to make some payment.

On Jan. 20, 1984, the day before the lottery board approved two contracts for Cho worth nearly $50,000, Cho gave the man a $5,000 check.

Several weeks later, Exum met the man at a downtown restaurant and they agreed to seek $50,000 from Cho, which they would split evenly. The next week, the man told Exum that Cho had paid him $1,000 and he gave Exum $500.

Cho later asked Exum if he had received the $5,000, and Exum said he had not. In March, Cho made the first of three cash payments to Exum totaling $5,000. The final two payments were made after Exum left the lottery board.

In April 1984, Cho bought a new $12,877 1984 Honda Accord for Exum's use. Eisenberg said the car was returned to Cho in November 1984 after the lottery board began investigating its use.