Thomas, 33, played just 18 games with the Mavs last season before leaving the team to be with his ailing wife. He never disclosed his wife's illness, but she is apparently doing well enough for Thomas to return to the league. Both sides handled last season's situation in good faith and want to continue the relationship.
"We're looking forward to visiting with him to see if he's ready for the challenge," said Mavs president of basketball operations Donnie Nelson. "It was a good situation for both of us last year."
ESPN.com's Marc Stein first reported in late July that Thomas and the Mavs were working on a deal.
"If all goes well, we'll reach an agreement," Bob Myers, Thomas' agent, said Monday.
The Mavericks are hoping the 6-foot-10, 240-pound Thomas can back up Dirk Nowitzki at power forward.
Though Thomas has power forward size, he has averaged only 4.1 rebounds -- to go with 11.5 points -- per game in 13 NBA seasons. He is a career 36.9 percent shooter from 3-point range, however.
Myers said Thomas is not talking with any other teams. If the Mavs and Thomas reach a deal, Dallas' roster will hit 14, leaving one spot available.