Thomas sat out for 11 months after he underwent an arthroscopic procedure to address his problematic hip. His last NBA game was March 22 as a member of the Los Angeles Lakers.
Sources told ESPN that Thomas made the choice to play Wednesday morning after he went through a 5-on-5 practice Tuesday and participated in a shootaround the next day. The Nuggets upgraded Thomas to questionable for their game against the Kings, later declaring him "ready" on social media.
"I got a goal that I want to reach," Thomas said to the Denver Post. "I want to be one of the best players that ever played the game. There's no quit in me. This is just a part of my story."
The 30-year-old Thomas will return to a Nuggets team that is within three games of the first-place Golden State Warriors in the Western Conference.
Thomas averaged 28.9 points per game with the Boston Celtics in the 2016-17 season and was a second-team All-NBA selection. He suffered a setback with his right hip that cut short his playoffs in 2017. The Celtics dealt him to the Cleveland Cavaliers later that summer.
Thomas joined the Lakers after a trade-deadline deal with the Cavaliers. He played only 15 games in the 2017-18 season.