It matched the second-highest scoring game of Speights' career and was his best total since 2009.
Klay Thompson scored 20 points and Stephen Curry added 15 for the Warriors (10-2), who won despite shooting a season-low 35.5% from the field. Thompson and Curry, two of the top 10 scorers in the league, combined to make just 11 of 35 shots.
Reggie Jackson had 22 points, 11 rebounds and eight assists, and Anthony Morrow added 16 points and matched a career high with 12 rebounds for Oklahoma City. Serge Ibaka scored 16 points, but shot just five for 17 for the Thunder (3-13), which lost its sixth in a row.
Curry was fouled with 16 seconds left and the Warriors up by two. Curry, who had made 47 of his first 49 free throws this season, missed the first and made the second to give Golden State an 89-86 lead.
Jackson drove and found Andre Roberson, who missed everything on an open three-pointer. Thompson was fouled and made two free throws with 5.7 seconds remaining to put away the game.
at Miami 94, Charlotte 93: Luol Deng scored 26 points, Chris Bosh and Mario Chalmers each added 20 and the Heat held on in the final seconds to beat the Hornets and snap a three-game home slide. Kemba Walker missed two potential go-ahead shots in the final half-minute for the Hornets, and Al Jefferson's tipin try bounced off the rim as time expired as Charlotte dropped its fifth straight.
Portland 94, at Boston 88: LaMarcus Aldridge had 20 points and 14 rebounds, reserve Chris Kaman scored 16 points and the Trail Blazers extended their winning streak to seven games with a victory over the Celtics. Damian Lillard added 12 points and five assists for Portland, which began a brief East swing. Jeff Green and Jared Sullinger had 19 points apiece for Boston, which dropped its fifth in six games.