Thomas even received fan mail from the stars. Soon after her marriage to actor John Agar in 1950, Shirley Temple wrote: "John and I want you to know that we are very grateful to you for the manner in which you handled the story on our wedding."
Some sent telegrams: "Thanks for sending the article to me; I got a kick out of reading it," Jimmy Durante wrote via Western Union in 1951. "Boy, you're great."
But Thomas also had his share of run-ins.
Doris Day and Frank Sinatra went months without talking to him after he quoted them candidly in stories, and Tracy cut off contact for years when something Thomas said about him offended the Oscar-winning actor. The fiercely private Brando never spoke with him again after Thomas published the biography "Marlon."
His encyclopedic knowledge of the industry was well appreciated by his colleagues. A former AP editor, Jim Lagier, would recall that Thomas had a filing system at his home that rivaled that of any news bureau.
"Because if you call Bob Thomas at two o'clock in the morning and say, 'Bob, Mary Smith has died,' he would say, 'Mary Smith,' and then, suddenly you could hear the filing cabinets were opening. He would start dictating the lead," Lagier told the AP in 2008 during an oral history interview.
Kathleen Carroll, executive editor of the AP, worked with Thomas in the Los Angeles bureau in the early 1980s.
"Bob was an old-fashioned Hollywood reporter and he knew absolutely everyone," she said. "He had a double-helping of impish charm with the stars, but back at the office, he was the quiet guy who slipped into a desk at the back and poked at the keyboard for a while, then handed in a crisp and knowing story soon delivered to movie fans around the world.
"Some days, you'd even get a smile out of him before he headed out the door again."
Through the years, Thomas' enthusiasm for his profession never waned.
"I get to interview some of the most beautiful people in the world," he said in 1999. "It's what I always wanted to do, and I just can't stop doing it."
Thomas is survived by his wife of 67 years, Patricia; daughters Nancy Thomas, Janet Thomas and Caroline Thomas; and three grandchildren.