The Celtics shot 62 percent in the first half and ran away with the game in the second quarter when they went 18 for 21 from the field (86 percent) and closed with a 26-7 run. Thomas scored all 14 of his first-half points - including four 3-pointers - during that stretch.
Jae Crowder had 19 points, Evan Turner scored 12 and David Lee 11 for the Celtics, who took the opener of a home-and-home set between the Atlantic Division rivals. Boston won for the fourth time in five games and pulled to 3-3 at home.
The 25-point margin of victory was the largest of the season for the Celtics.
The Nets (2-11) shot 42 percent in the first half and turned the ball over 11 times, including four times during Boston's second-quarter spurt. It was the ninth time this season they were held under 100 points.
Thaddeus Young had 14 points and 10 rebounds for the Nets, his fifth double-double after posting three last season. Brook Lopez also scored 14 points, and rookie Rondae Hollis-Jefferson added a career-high 13.
Nets: Lopez and Shane Larkin were the only two Nets to shoot better than 50 percent. ... Lopez has led the team in scoring eight times this season. ... It was the Nets' worst shooting performance and defensive effort of the season. They shot 39 percent to 59 percent for Boston.
Celtics: All seven of Boston's wins have been by at least 13 points. ... The Celtics scored 66 points in the first half, their second-most this season. They had 72 in a Nov. 6 win over Washington. ... G Marcus Smart left in the fourth quarter with a bruised right knee.
Nets: Host Boston on Sunday.
Celtics: At Brooklyn on Sunday.