Thomas died earlier this month following an accident while working on the job at a tire manufacturing plant in Oklahoma ... according to his wife, Jessica Wells.

We're told part of Thomas' body was caught in a machine, described to us as an automatic conveyer belt type of machine which did not stop, and he was rushed to a nearby hospital in Idabel, OK.

Thomas' wife says he was then airlifted to a bigger hospital in Tyler, Texas ... because doctors thought specialists in Tyler might be able to help him.

Ultimately, we're told Thomas died in the hospital in Tyler back on November 13.

You may have seen Thomas singing his heart out on TV ... he appeared on "America's Got Talent" as well as "The Voice" and "The Winner Is" ... in addition to 'X Factor.'

Thomas got into music at an early age, teaching himself to play instruments by ear and singing choir at church and in school in Oklahoma. He mostly sang hymns and contemporary music.

His wife of 17 years is remembering him as a unique person who always had a smile on his face and tried to make people laugh. She says he would sometimes bust out singing and didn't mind the spotlight.

Thomas was 46.