According to NFL Network's Ian Rapoport, the Seahawks were "specific and clear" in telling Thomas that they would not address his contract regardless of whether he reported to training camp.
Thomas was not present when camp opened Thursday.
The 29-year-old Thomas is set to enter the final year of his contract in 2018 with a base salary of $8.5 million, per Spotrac.
According to ESPN's Adam Schefter, the "belief around the league" is that Thomas will hold out for the entirety of training camp and potentially into the regular season unless he is traded or given a new contract.
Late last season, Thomas' actions following a win over the Dallas Cowboys suggested he may not have been happy in Seattle.
Per Jon Machota of the Dallas Morning News, Thomas entered the Cowboys' locker room after that game and told head coach Jason Garrett, "If y'all have the chance, come get me."
The Orange, Texas, native is a six-time Pro Bowler, three-time All-Pro first-teamer and one-time Super Bowl champion.
The eight-year veteran didn't miss a single game over the fist six seasons of his career, but he sat out five contests in 2016 and two last season.
Despite his recent injury issues, Thomas was named to the Pro Bowl last season after registering 88 tackles, six passes defended and two interceptions.
With Richard Sherman now in San Francisco and Kam Chancellor unlikely to play another NFL game, Thomas is the final remnant of the Legion of Boom secondary.
If he is not in the Seahawks' lineup in Week 1 of the regular season, a combination of Maurice Alexander, Akeem King, Bradley McDougald, Tedric Thompson and Delano Hill is expected to handle the workload at safety.