Smith became the franchise's first player in history to score at least 30 points from off the bench in three consecutive contests.
New York won its seventh straight and Smith has averaged 26.4 points a game during that stretch. He made 12-of-18 from the field and hit 11-of-12 from the foul line.
Carmelo Anthony added 32 points with 11 rebounds, helping push New York to an 18-point lead after one quarter.
Gerald Henderson scored 35 points for Charlotte, which remained stuck on a league-low 17 wins for the season.