The Saints didn't release terms of either deal.
Thomas missed 10 games last season because of a severe left ankle sprain. He gained 269 rushing yards and scored two touchdowns in the six games he played.
Thomas, who in 2007 made the Saints' roster as an undrafted rookie free agent out of Illinois, emerged as the team's top rusher in 2008 and 2009. He also has been effective on screen passes, on which he scored touchdowns in both the NFC title game and Super Bowl two seasons ago, and he has filled in on kickoffs when needed.
"Glad to be back whodat fans!" Thomas posted on his Twitter page. "Let's get another ring!!"
Four of Hartley's misses came from 39 yards or closer. Beyond that distance, Hartley made eight of nine kicks, hitting both from 50 or more yards.
During the playoffs two seasons ago, Hartley hit the winning field goal in the NFC Championship Game, then became the first NFL kicker to connect on three field goals of 40-plus yards in a Super Bowl.
The Associated Press contributed to this report.