NEW YORK (AP) _ An 82-year-old voice coach who plunged to his death from the upper balcony of the Metropolitan Opera House during a performance of ''Macbeth'' had told his niece that he was going to kill himself at the opera, the New York Post said today.

The newspaper said Bantcho Bantchevsky telephoned his niece, Dr. Lada Manolova, on Friday, the night before he died.

''He told me, 'You know what? I find a way how to kill myself,''' the Post quoted the niece as saying. '''I want to go in the opera and jump from the balcony and I kill myself.'''

The woman said her uncle had been severely depressed and in poor health since being hit by a bus two years ago. She said he had made suicide threats before.

''Once he said he would jump from his apartment. Once with a knife - but he was not strong enough to do this,'' she said.

After an autopsy and investigation, the city medical examiner ruled Bantchevsky's death a suicide, Ellen Borakove, speaking for the medical examiner's office, said Sunday.

Bantchevsky, a native of Bulgaria who lived just a block from the opera house, plunged 80 feet from the Family Circle balcony into the rear of the orchestra section amid screams from the opera patrons.

The fall took place during the intermission between the second and third acts of the Giuseppe Verdi opera based on Shakespeare's ''Macbeth.'' At the time, many of the 3,800 in the packed house were in the lobbies.

The opera was being broadcast live to a nationwide radio audience and the remainder of the performance was canceled after the fall.

Witnesses said Bantchevsky bounced off a lower balcony rail, landed on unoccupied seats near the left center aisle 10 rows from the back of the orchestra and then fell into the aisle under a broken seat.

A 71-year-old woman was grazed by his body, but was unhurt, according to police.

Bantchevsky had been involved in a minor disturbance during the first intermission and was leaning over the balcony rail, high school teacher Joe Panarello said.

''I saw him being restrained by an usher,'' he said.

''Ushers knew him well,'' said opera spokeswoman Johanna Fiedler. ''They recognized him right away.''

Panarello said he thought, ''My God 3/8 It's the curse of Macbeth.''

''Macbeth'' is considered a cursed play by actors because of the many accidents that have taken place during performances. Some actors will not mention the drama by name backstage, superstitiously referring to it as ''the Scottish tragedy.''

Gilbert Bloom, a neighbor, described Bantchevsky as an elegant gentleman who wore a beret and spoke with the remains of a European accent.

''He was a very, very immaculate dresser, but in an old style,'' Bloom said.

He said Bantchevsky lived alone and never spoke of a family. He had been having heart trouble in recent years, but Bloom said he hadn't thought Bantchevsky would commit suicide.

Operagoers were told that arrangements would be made for substitute tickets.