Thomas was born in Woodington, Darke County, Ohio, to Harry and Harriet (nee Wagoner) Thomas. His father was a doctor, his mother a teacher. In 1900, the family moved to the mining town of Victor, Colorado. Thomas worked there as a gold miner, a cook, and a reporter on the newspaper.

Thomas's most amusing on-air gaffe occurred during one of his daily broadcasts in the early 1960s. He was reading a story "cold" (going on the air without pre-reading his copy, contrary to his usual practice) which contained the phrase "She suffered a near fatal heart attack". The line came out of Thomas's mouth as "She suffered a near fart ... err fatal heart attack". Realizing instantly what he had said, he tried to continue but eventually collapsed into gales of laughter, which continued into - and beyond - his announcer's chuckling sign-off for the day. Thomas' long-time friend and ghostwriter Prosper Buranelli wrote the nightly newscasts. The day's script was sent by teletype to Thomas' home in Pawling, NY from which he usually did his broadcast. One evening, Buranelli's final story was about an actress going into a Los Angeles hotel with a Great Dane. The dog's tail got caught in the revolving door and she sued the hotel for $10,000. Buranelli added a comment to the story to give Thomas a laugh before going on air, but Thomas read the story as written with Buranelli's comment, "Who ever thought a piece of tail was worth 10 grand?" Another on-air mishap had Thomas reading a story about President Eisenhower's visit to Hershey, Pennsylvania "where he was greeted by the folks who make chocolate bars, with and without nuts." ("Nuts" is a euphemism for "testicles.") As Thomas read the next story, he could hear the announcer breaking up with laughter in the New York City studio, which caused Thomas to break up, as well. Air checks of some of Thomas' gaffes (as well as recreations of his "bloopers") are available to collectors.

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He was reading a story "cold" (going on the air without pre-reading his copy, contrary to his usual practice