BOSTON — Isaiah Thomas warmed up with 18 points in the first three quarters and then did his usual fourth-quarter thing, powering his Boston Celtics to a 108-98 victory over Charlotte that sent the Hornets to their fifth straight loss Monday night.

Boston’s little big man, the NBA’s leading fourth-quarter scorer at 9.9 points per game coming in, scored 13 of his 17 fourth-quarter points in a span of 4:03 as the Celtics built a 13-point lead and then held off the Hornets for their seventh win in their last eight games. Boston (26-15) improved to 13-3 since Thomas returned after missing four games due to a groin strain.

Thomas looked at his watch (for fourth-quarter time, his new trademark) on at least one occasion in the quarter.

His 35 points, including two late that came on a long jumper from the right corner with 7-footer Cody Zeller on him, were above the 31.3 points per game he was averaging in the 15 games coming in.

His last two baskets stymied the Charlotte comeback after the Hornets closed to within four with 2:43 left.

Thomas was 7 of 15 from 3-point range, his team going 15 of 39 from behind the arc and winning a game despite taking just 10 free throws, four of them in the final 18.5 seconds.

The Hornets, led by Kemba Walker’s 24 points (despite just 8-of-21 shooting from the floor), dropped all five games of their road trip to fall to 20-21 — 12-18 since an 8-3 start.

Boston’s Al Horford scored 22 points and added six rebounds and four assists. Kelly Olynyk had his second straight big game off the bench with 15 points, nine rebounds and four assists, and Jae Crowder contributed 15 points, seven rebounds and three assists.

Marvin Williams had 21 points, Zeller 13 and eight rebounds and Nicolas Batum eight points, 10 rebounds and 10 assists for the Hornets, who are 0-3 against the Celtics this season.

The Celtics outrebounded Charlotte 44-42, improving to 12-0 when tying or leading an opponent in rebounds.

NOTES: Celtics G Avery Bradley, who missed four games with an Achilles strain, returned, and F Kelly Olynyk, who rolled his right ankle before Sunday’s practice, also played. … The Hornets were without injured G Jeremy Lamb (inflamed metatarsal). … Boston C Tyler Zeller missed his seventh straight game because of illness, missing the latest game against his brother, Cody. … Both teams wore T-shirts honoring Martin Luther King’s “Never Stop Dreaming,” and Celtics rookie Jaylen Brown addressed the crowd in a moving salute to Dr. King. … The Hornets open a five-game homestand against the Portland Trail Blazers on Wednesday. Boston hosts the New York Knicks the same night.