The Magic have now lost eight consecutive games and their last 10 regular-season games in Boston.
Ignited by Olynyk, who scored nine of his points in the fourth quarter, the Celtics seized control by starting the period on a 22-4 run and pushing their lead as high as 27.
Nik Vucevic led Orlando with 14 points and eight rebounds. Shabazz Napier added 13 points.
The Magic struggled offensively all night, committing 16 turnovers that led to 22 points by the Celtics.
Thomas, playing in his first game since being named an All Star, was able to rest in the fourth quarter. He sat out practice Thursday and played Friday on a sore right ankle.
One segment that underscored how bad things were for the Magic came with just over five minutes to play in the third quarter.
Trailing by six, Victor Oladipo was fouled on a 3-point attempt but missed all three free throws. The final miss ignited a fast break for the Celtics and a 3-pointer by Jae Crowder.
Orlando stumbled into many of its old habits in the first half as the Celtics' lead grew as high as 13.
Magic forward Tobias Harris in particular took some rushed shots, at one point hitting nothing but the backboard on a 3-point attempt on a fast break.
Boston shot 52 percent from the field (21 of 40) and connected on five 3s.
Celtics: Have scored at least 100 points in 11 consecutive games for the first time since the 1995-96 season. … Entered the night averaging 104.4 points per game, the team's highest since the 1991-92 season, when it averaged 106.6 points.
Magic: Vucevic scored at least 10 points for the 38th time this season. … Are 1-12 so far in 2015. … Signed guard Keith Appling to a second 10-day contract. Before joining the Magic with his first 10-day contract on Jan. 18, he played in 17 games this season with the Erie BayHawks of the NBA Development League, averaging 16.8 points.