Thomas, who was a free agent, will provide depth for the 49ers after they lost Reggie Bush for the season with a torn MCL when he slipped and fell on the concrete at Edward Jones Dome in St. Louis. Thomas, who most recently played for the New Orleans Saints, came close to a deal with the Houston Texans in the preseason, but negotiations fell apart.
Former Browns back Shaun Draughn will also join Thomas.
Thomas spent eight seasons with New Orleans and is the fourth-leading rusher in Saints history with 3,745 yards. He went undrafted out of Illinois in 2007. The Thornton Fractional South product led the Illini in rushing for three seasons. In 40 games, he ran for 2,545 yards and 20 touchdowns with 4,451 all-purpose yards good for second all-time in school history at the time.