The Hall of Famer had been working as a special consultant to Milwaukee Bucks ownership since 2015.
Thorn famously drafted Michael Jordan with the third overall pick in 1984 as general manager of the Chicago Bulls.
The 78-year-old also chaired USA Basketball's selection committee for the Dream Team prior to the 1992 Olympics.
Thorn's best success as an executive arguably came with the then-New Jersey Nets. He spent eight seasons as general manager of the club, leading the franchise to its first NBA Finals appearances in 2002 and 2003.