The Seahawks selected the 25-year-old 14th overall in the 2010 Draft, and he has become the best player at the safety position in the league in that timespan, having been named as an All-Pro for the past three years.
Thomas also secured the most lucrative contract signed by a safety when he extended his deal with Pete Carroll's side during the off-season.
He wrote on his website: "Anyone who is trying to change the face of anything has to set a new standard.
"That was my goal from day one in the NFL. I wanted to change people's perceptions of the safety position. Safety has been an unappreciated position in the league for a long time.
"It's proven to be an invaluable position, especially for our defense in Seattle."
Thomas has recorded 345 tackles, five forced fumbles and 15 interceptions in his four-year NFL career.