Kawhi Leonard poured in 26 points in just 24 minutes for the defending NBA champions, who dominated from start to finish.
The Thunder suffered their fourth straight defeat and fell out of the eighth and final Western Conference play-off spot.
The Thunder fell one half-game behind New Orleans in the race for the eighth seed after the Pelicans defeated Golden State 103-100 on Tuesday evening.
Desperate for a victory, the Pelicans rallied from 14 points down to stun the Warriors, who have clinched the top seed in the West. Anthony Davis scored a game-high 29 points to lead the Pelicans.
In Oklahoma City, the Spurs were led by Leonard, who connected on 10 of his 15 attempts from the floor, the Spurs shot 52.8 percent from the field.
Their eighth successive victory tightened the race for the Southwest Division title. They are now 1 1/2 games behind division leaders Houston and one half-game behind Memphis.
Russell Westbrook finished with 17 points and six steals for Oklahoma City, but no other Thunder player scored more than 11 points.
The good news for Oklahoma City as they battle for a playoff berth is that three of their last four games of the regular season are against teams with losing records: Sacramento, Indiana and Minnesota.
Elsewhere, the Atlanta Hawks, who set a team record with 19 straight wins earlier in the season, now also own the franchise mark for victories in a season with their 58th success, a 96-69 win over Phoenix
DeMarre Carroll made all but one of his nine shots and the Hawks held the Phoenix Suns to 31.3 percent shooting.
Goran Dragic led a balanced effort with 28 points and five assists as the Miami Heat defeated the Charlotte Hornets 105-100 in a pivotal game in the race for one of the Eastern Conference’s final playoff berths.
Atlanta 96-69 Phoenix
Miami 105-100 Charlotte
New Orleans 103-100 Golden State
San Antonio 113-88 Oklahoma City
Sacramento 116-111 Minnesota
L.A. Clippers 105-100 L.A. Lakers