"I knew there was going to be a lot of money on the table, but I play this game because I really do love it," Thompson said before scoring a career-high 41 points in Saturday's 127-104 home-opening win against the Los Angeles Lakers. "It's a blessing to have the deal I got, and I'm going to do everything I can to go out there and prove I'm worth it."
Sources told ESPN.com that the four-year deal is a maximum contract projected to be in the $70 million range, with the specific numbers to become known in July when the NBA announces the exact 2015-16 salary cap.
"I've never see a team rally around a player so much to get him paid," Warriors general manager Bob Myers said. "It says a lot about Klay and what he means to this franchise."
Myers called the contract the latest commitment from ownership to build a championship contender and Thompson the kind of player who will help the Warriors reach that goal.
There is no opt-out clause for either side in the extension, keeping Thompson under contract through the 2018-19 season -- longer than any other player on the team and through the franchise's planned move to a new arena across the bay in San Francisco.
The Warriors have gone to great lengths to hold on to Thompson, refusing to include him in trade talks for Kevin Love this summer. They also rebuffed several recent inquiries for him as extension talks dragged on.
Ultimately, Golden State decided to lock up the 24-year-old guard, who teams with Stephen Curry to form one of the best backcourts in the league.
Thompson averaged 18.4 points last season, second on the team to Curry and a career high.
Myers said he was negotiating this week with Thompson's agent, Bill Duffy, when the general manager looked out of his office window and noticed Thompson was the only player still at the practice facility taking shots after hours.
"This contract is well deserved," Myers said. "And I think that's the best compliment I can give Klay."
The Warriors had until midnight Friday to reach an agreement with Thompson, who would have become a restricted free agent next summer otherwise.
Information from ESPN.com's Marc Stein and Ramona Shelburne and The Associated Press was used in this report.