In one of his previous professional incarnations, John Jay Hooker was into fried chicken. In another, it was politics. Later, it was motor oil. Now the flamboyant Nashville lawyer is off in yet another direction as chairman of United Press International, a venerable but struggling journalistic institution.

Hooker, who last week bought into the company that owns UPI, says the news service, which appeared to be in danger of dying a year ago, is "wonderfully positioned" to take a profitable place in the "communications revolution that is going to change the world. This is a tremendously interesting time for an entrepreneur, and that's what I am."

As long-time counsel for the Nashville Tennessean and later publisher of its arch-rival Nashville Banner--a newspaper that vehemently opposed him in his three unsuccessful campaigns for statewide elective office in Tennessee--Hooker became familiar with the news business, and says he likes it.

But he said in a telephone interview yesterday that his involvement with UPI will be in "major policy questions" such as new business opportunities, while day-to-day editorial management will remain under the present team. Hooker said he would have "input" into such crises as the recent expulsion of UPI's correspondent in Poland, but he said he would have "virtually nothing to do with the day-to-day news. We have professionals to do that. I'm not an editor."

Hooker said he had carefully checked UPI's once-shaky financial status and found it promising. As a part of the privately held Media News Corp., UPI is not required to disclose earnings. A spokesman for the news service said it still is losing money--as it has for years--but he said it is positioned to make a profit as early as 1984.

At the end of last year, UPI was signing up more new clients than it was losing, reversing a decline that lasted many years, the spokesman said. Most are radio and television stations, but two major newspapers have subscribed--the Philadelphia Inquirer for the first time, and the New York Daily News after having canceled it.

He said that UPI commissioned a market study by Yankelovich, Skellky & White, which showed that the agency fared poorly by comparison with the Associated Press in its coverage of state, local and regional issues. To cure that, UPI has reorganized its domestic news staff and has assigned each of six regions in the nation its own Washington correspondent, he said.

By the end of next year, UPI expects to be transmitting to all 5,400 domestic clients by satellite instead of land lines, saving about $5 million a year in communications costs and thereby becoming profitable, the spokesman said.

Hooker, 52, is known as a fast talker and a flashy dresser. Born rich, he has one of those colorful, larger-than-life personal histories that seem to flourish in the South.

He once headed the Minnie Pearl chain of fried chicken restaurants, now defunct. He was chairman of STP Corp., the manufacturer of engine-oil additives. He was a personal friend and political ally of the Kennedy family. He hobnobbed with Mohammed Ali. He was a co-founder of LIN Broadcasting Co., an operator of radio and television stations, and of Hospital Corp. of America. And he negotiated an exchange of tractors to Cuba for prisoners taken in the Bay of Pigs invasion.

He got into UPI, on what he said was his third attempt, by buying out for an undisclosed amount the shares of Len R. Small, a Moline, Ill., newspaper executive, and Cordell J. Overgaard, a Chicago lawyer.