Seahawks general manager John Schneider, speaking at a charity event Thursday night, said he received assurances from Thomas' representatives that Thomas will not be a no-show at training camp, per the Seattle Times.
Thomas, the subject of multiple trade rumors during the offseason, did not attend the team's voluntary offseason program.
The three-time All-Pro safety posted on Twitter last month that "I want to be a Seahawk" but also told a Seattle radio station that he planned to be "rich and happy regardless ... whether I'm in Seattle or anywhere else."
Schneider has acknowledged listening to trade offers for Thomas but Seahawks head coach Pete Carroll made it clear Thursday that Thomas is an integral part of the team's foundation and he expects him to be at training camp.
"He's a Seahawk," Carroll said. "I don't know what everyone's talking about. ... He better be there. He's on the roster. We're counting on him."
Thomas is set to make $8.5 million in base salary in 2018 and is lobbying for a new contract, hinting that he would be willing to hold out if necessary.
Schneider acknowledged he has not talked to Thomas' representatives since the NFL Combine, but noted that was not unusual.
Seattle has undergone a roster purge in the offseason, parting ways with star cornerback Richard Sherman, defensive end Sheldon Richardson, wide receiver Paul Richardson, tight end Jimmy Graham and defensive end Michael Bennett.