Siakam scored 25 of his points in the first half and also had 12 rebounds overall as the Raptors won their eighth straight game at home.
"I just feel energized," said Siakam.
Serge Ibaka delivered 16 points, Fred VanVleet chipped in with 14 points, seven rebounds and seven assists, and Terence Davis had 14 points off the bench in front of a crowd of 19,800 at the Scotiabank Arena.
Devin Booker scored 21 points and had eight assists and Deandre Ayton tallied 17 points and 10 rebounds for the Suns, who have lost seven of nine.
Ricky Rubio had 13 points and nine assists, and Kelly Oubre scored 11 points in the loss.
"They set the tone early," Suns guard Ricky Rubio said. "That's why they're a championship team."
TJ Warren scored 27 points to lead the Pacers, who outscored the Knicks 65-45 in the second and third quarters.
The Knicks held Indiana to just 12 points in the opening quarter but the Pacers recovered to shoot 53 percent from the field in the second and third. Indiana managed to pull out the victory despite missing 15 of 20 shots in the fourth quarter.
Domantas Sabonis posted his 42nd double-double with 24 points and 13 rebounds and Doug McDermott came off the bench to score 14 points for the Pacers, who won their second consecutive game after losing six straight.
Victor Oladipo finished with eight points in little more than 25 minutes before exiting with back soreness.
Bobby Portis scored 19 points to lead the Knicks, who lost their third straight game.
Rookie RJ Barrett added 17 points and Frank Ntilikina contributed 14 but leading scorer Julius Randle was held to just nine points in the loss.
Luka Doncic flirted with a triple double, scoring 33 points, grabbing 10 rebounds and handing out eight assists as the Dallas Mavericks toppled the Orlando Magic 122-106.
Maxi Kleber did much of his damage in the fourth, hitting three three-pointers and scoring 12 points in the quarter.
He sparked a critical final quarter for the Mavericks, who also dominated in the opening quarter.
In Washington, Collin Sexton scored 25 points as the Cleveland Cavaliers posted a 113-108 victory over the Wizards, making JB Bickerstaff a winner in his Cavaliers' head-coaching debut.