Thomas, whose works include biographies of celebrities including Walt Disney, Joan Crawford and Fred Astaire, died Friday of age-related causes, the Los Angeles Times reported Friday.
Thomas began covering Hollywood for the AP in 1944 and became well known for covering the film industry and the marriages, deaths and scandals of its stars. He became a familiar face around studio backlots and was known to file up to six columns per week.
The reporter was only a few steps behind Robert F. Kennedy when the Democratic presidential hopeful was shot and killed at the Ambassador Hotel in Los Angeles in June 1968.
"I heard the shots and ran into the kitchen and saw that ghastly scene," Thomas told the Los Angeles Times in a 1990 interview. "Rosey Grier, I think it was, was holding Bobby's body."
Thomas, who competed in a friendly rivalry for more than 40 years with UPI entertainment reporter Vernon Scott until his death in 2002, said his favorite interview subjects were Joan Crawford and Humphrey Bogart.
They always had something to say, and Bogie loved to be controversial," Thomas told the Times during the 1990 interview. "He'd call me up in the middle of the night and say, 'Let's touch a nerve.'"
Thomas is survived by his wife, Patricia, who he married in 1947, as well as daughters Nancy, Janet and Caroline and three grandchildren.