Thomas had one season left on his deal, which would have paid him nearly $6.5 million. He played in just 18 games with the Bulls after being acquired from the New York Knicks in a four-player trade on Feb. 19.
The 32-year-old Thomas has averaged 11.6 points and 4.1 rebounds for six teams in 12 years. He was also dealt from the Knicks to the Bulls before the 2005-06 season, but played just three games for Chicago and was waived the following March.
Information from The Associated Press was used in this report.