The younger son of head coach John Thompson, Ronny Thompson saw action in four seasons as a capable walk-on, having averaged 18 points per game at Flint Hill Prep as a senior.

Thompson was most productive in his first two seasons at Georgetown, tying career scoring bests of 11 points versus Syracuse in the 1988-89 season and North Carolina in the 1989-90 season. Thompson averaged 41 percent from two point range but just 26 percent from three point range, and his playing time was limited as an upperclassman with the arrival of Joey Brown and Charles Harrison in 1990.

Following a year on Wall Street after graduation, Thompson joined the coaching ranks as an assistant at Oregon in 1993. He spent two years at Loyola (MD) and two years at the Philadelphia 76ers before joining his father's staff in 1998 during John Thompson's final season as head coach. Thompson served as the lead assistant for Craig Esherick from 1999 to 2003 but actively sought to be a head coach; when it was clear Georgetown wasn't interested in replacing Esherick with him, Thompson left Georgetown for Arkansas in 2003 and took Esherick's #1 recruit, center Darian Townes, with him.

In 2006, following three seasons at Arkansas, Thompson was named head coach at Ball State. The 9-22 season was a disaster, with Ball State officials accusing Thompson and his staff of NCAA violations. Thompson was fired at the end of the season and was paid $200,000 in a negotiated buyout.

Thompson reappeared in 2017 as a shadow advisor to head coach Patrick Ewing, though he was never publicly identified by the University as such until five years later, when Ewing gave him the title of Chief of Staff. A polarizing figure outside the basketball office, he was dismissed upon Ewing's departure.