DALLAS (AP) _ The Dallas Times Herald, a daily in one of the nation's most competitive newspaper cities, is being sold for the second time in a year and a half.

MediaNews Holdings Inc., controlled by Times Herald Chairman William Dean Singleton, plans to sell the paper to DTH Media Inc., a new corporation controlled by MediaNews stockholder John Buzzetta, both parties said.

Rumors had been circulating for weeks about the pending sale of the Times Herald, which has had marginal profits in the face of a weak state economy and tough competition from the larger newspaper, The Dallas Morning News.

Buzzetta, 38, has been associated with Singleton, 37, since 1977. Buzzetta is president and majority stockholder in the Scrantonian Tribune of Scranton, Pa.

Singleton and a partner, Richard B. Scudder, acquired the Times Herald, the second-largest paper in Dallas, in late 1986 for $110 million from Times Mirror Co. As part of the deal, they received $7 million that the newspaper had in the bank, as well as a $20 million discount for paying early, to bring their total cost to $83 million.

Singleton, who was in Denver Tuesday in meetings at The Denver Post, which he also owns, said in a statement that proceeds from the transaction will go toward retiring debt and for new acquisitions.

The sale comes as the young entrepreneur has extended himself financially to purchase The Houston Post; The Gloucester County Times in Woodbury, N.J.; and Today's Sunbeam in Salem, N.J., which he owns through MediaNews Holdings, a holding company under Media News Group. Media News Group includes Garden State Newspapers, which owns 16 medium-sized dailies.

Specific terms of the Dallas deal were not disclosed, but Buzzetta said, ''A substantial amount of cash and stock was involved in the transaction.''

Buzzetta said DTH Media Inc. will have a controlling interest while MediaNews will retain a financial interest in the newspaper and will remain a stockholder.

''The Dallas Times Herald is currently showing a healthy annual operating profit,'' Buzzetta said in a statement.

''We're buying a winner and we intend to operate the Dallas Times Herald in the proud tradition that has kept it successful for more than 100 years,'' he said.

Buzzetta said no layoffs are planned in the Times Herald newsroom.

In his statement, Buzzetta said he would become publisher of the newspaper and Art Wible, publisher since 1985, has agreed to leave.

Three Times Herald executives, editor Dave Burgin, executive vice president and general manager Robert Hollingsworth and senior vice president and chief financial officer Richard L. Jacobs will join MediaNews Group.

Singleton said in his statement, ''The proposal was attractive enough financially that it had to be considered seriously.''

Earlier reports said Singleton was negotiating to sell the paper for $140 million.

Two weeks ago, the Dallas Morning News and the Dallas Times Herald agreed to drop lawsuits filed against each other concerning paid circulation figures.

Latest figures released through the Audit Bureau of Circulation for the six months ended Sept. 30, 1986, showed the Times Herald's daily circulation was 246,370 and The Morning News' was 390,987. On Sunday, the Times Herald's reported paid circulation was 338,963, and the Morning News reported 531,417.

The next ABC report, for the period ending March 31, 1988, is expected in late summer.

Newspaper industry analysts said resolving the circulation dispute was integral to a sale of the Times Herald.

''I don't think you'd buy a newspaper without having circulation figures resolved,'' said John Reidy of Drexel Burnham Lambert Inc. in New York. ''This way you don't have two guys suing each other and confusing the advertisers.''