Thomas told ESPN's Josina Anderson he will end his holdout and report to the Seahawks' facilities Wednesday.
He skipped all of Seattle's training camp and preseason while holding out for a new contract.
Thomas wrote Wednesday on Instagram:
"I worked my whole life for this..... I've never let me teammates, city or fans down as long as I've lived and don't plan on starting this weekend. With that being said, the disrespect has been well noted and will not be forgotten. Father Time may have an undefeated record but best believe I plan on taking him into triple overtime when it comes to my career."
In an article on the Players' Tribune last month, Thomas explained why he was staying away from the Seahawks:
"If you're risking your body to deliver all of this value to an organization, then you deserve some sort of assurance that the organization will take care of you if you get hurt. It's that simple. This isn't new, and this isn't complicated. It's the reason I'm holding out—I want to be able to give my everything, on every play, without any doubt in my mind.
"And it's the reason why I'm asking the Seahawks to do one of two things:
"Offer me an extension.
"Or trade me to a team that wants me to be part of their future."
ESPN's Adam Schefter reported Wednesday the Dallas Cowboys offered a second-round pick for Thomas but were turned down because the Seahawks want more in a deal.
Thomas will earn $8.5 million in 2018, the final season of his four-year contract.
The Seahawks open the season Sunday at Mile High Stadium against the Denver Broncos.