There are hardly any good guys, but lots of sleazy bad guys, in "The Rothko Conspiracy," tonight's American Playhouse (at 9 p.m. on Channel 26). This 90-minute show is a ragged "dramatic reconstruction" of the legal battle over the multi-million-dollar legacy of the late Mark Rothko, the American abstract painter who slashed his arms and bled to death 13 years ago.

Rothko was a master. We know that from his canvases. He was also bitter, ambitious and street-smart. His suicide surprised his friends. But it won't surprise the audience. For the Rothko that the show portrays--Larry Hoodekoff plays him--is a bumbling loser.

Tears are always trickling from under his thick glasses. He yells at his young children. He drinks vast draughts of Jack Daniel's directly from the bottle and then, without the bother of rising from his chair, drinks again as deeply from a fifth of Smirnoff vodka. He mumbles and he whines. No wonder that this painter, this pitiful incompetent, is putty in the hands of his scheming art world friends.

A year before his death, Rothko appointed three of them--Bernard Reis, his accountant, Morton Levine, a professor of anthropology, and Theodoros Stamos, a fellow New York painter--executors of his will. Through negligence or avarice or both, or so the show contends, they ripped off the estate. They sold its paintings cheap, they played fast and loose with documents, they broke promises they made to Rothko's orphaned daughter, Kate, and they did so in conspiracy with the painter's dealer, Vienna-born Frank Lloyd of Marlborough Gallery, New York.

Kate Rothko sued the four of them. Eventually she won. On Dec. 18, 1975, New York Surrogate Judge Millard Lesser Midonick removed the three executors, canceled their contracts with Marlborough, ordered the return of 658 unsold pictures--and assessed the four defendants "jointly and severally" a total of $9,252,000 in damages and fines.

Dealer Lloyd is portrayed by Ronald Lacey as the baddest of these bad guys. Lacey is the actor who played the leather-coated, pig-faced Nazi sadist in "Raiders of the Lost Ark." As international dealer Lloyd, he is not much more likable. He puffs on huge cigars and glides around in limousines to show he only cares for money. "If it sells, it's art," he says. Occasionally he screams inexplicably as if he's slightly insane.

The Rothko that we meet here wants to keep all of his paintings. "How can I sell any?" he asks Kate. "They are my children." But if the real Rothko did not want to sell his pictures, why did he do business with Marlborough and Lloyd?

He did so, probably, because Lloyd at the time was the most successful dealer in the world. Marlborough handled the art of Jackson Pollock, David Smith, Franz Kline, Ad Reinhardt and other major artists of the New York school.

New York dealer John Bernard Myers, a man who knew the players, has written in "The New Criterion" that a year before the suicide, an old friend, Herbert Machiz, met a grinning Rothko on a New York street.

" 'You look like a cat who has devoured a mouse,' Herbert told him . . . 'Indeed, I have devoured a mouse,' Rothko replied. 'Which mouse?' asked Herbert. 'Well, not a mouse actually. A large tiger. I've just finished negotiating my newest contract with my dealer. Nothing gives an artist more pleasure than getting the better of a dealer . . .' " That dealer was Frank Lloyd.

It is, of course, not easy to draw a gripping drama from reams of legal papers. One feels this show exaggerates. True, the executors were venal (Reis and Stamos were associated with Marlborough), and Frank Lloyd was a sharpie. But Rothko deserves blame as well. After all, he picked his friends. This show portrays the painter as wholly innocent by virtue of his complete incompetence. But that will not really wash. "The Rothko Conspiracy," a production of BBC-TV and Lionheart Television, was written by Michael Baker and directed by Paul Watson.