The Celtics had lost two straight heading into their showdown with the Western Conference's top team.
Boston standout Thomas scored 25 points as the Celtics snapped a two-game losing skid Wednesday with a 99-86 victory over the Golden State Warriors in a battle between two NBA title contenders.
"We are fighters. We compete," said Thomas. "We are just a bunch of competitors. We wanted to win to end the losing streak."
The Celtics, who are fighting to hold onto the number two seed in the East, had lost two straight heading into their showdown with Golden State, the Western Conference's top team.
To add to their difficulties, leading scorer Thomas went public with criticism of coach Brad Stevens' coaching style after Monday's loss to the Los Angeles Clippers.
But the Celtics had reason to believe they can have success in Oakland. After all, on their last visit 11 months ago, they snapped Golden State's 54-game home winning streak.
Winning takes care of everything and Thomas was full of praise for Stevens on Wednesday.
"The coach is going to make his decisions. I believe in the coach. I trust every decision he makes and tonight we won," Thomas said.
Boston took charge after a dunk by Draymond Green that gave the Celtics an 80-79 lead in a game that featured eight lead changes and eight ties in the first 41 minutes.
Jae Crowder hit three-pointers on consecutive possessions during a 15-0 fourth-quarter surge that helped propel the Celtics to victory.
"We didn't want to turn the ball over. We believed in our guys and they did the job," Thomas said.
Boston improved to 41-24 on the season and won for the second time in four games on its Western trip. That allowed the Celtics to remain a game ahead of the Washington Wizards in the battle for the No. 2 playoff position.
The road-weary Warriors fell to 52-12 as they lost for the third time in five games and saw their lead over red-hot San Antonio atop the West cut to 1 1/2 games.
Golden State played without Kevin Durant (sprained left knee), who tallied 23 points to lead the Warriors to a lopsided win earlier in the season at Boston.
Durant, who is expected to be evaluated again in three weeks, spoke to reporters before the game.
"I hurt my knee. A lot of guys go through this," he said. "It is nothing to be concerned about. I got a boo boo playing basketball."
Klay Thompson scored 25 points and Stephen Curry scored 23 for the Warriors.
"We're in a tough spot in the schedule, obviously, and with KD's injury," said Warriors coach Steve Kerr.
Elsewhere, Paul George scored 21 points, Thaddeus Young had 18 points and eight rebounds and CJ Miles added 15 points, and the Indiana Pacers defeated the Detroit Pistons 115-98.
With the victory, Indiana avoided slipping to .500 and completed a four-game season series sweep of Detroit.
"It also was important tonight that we got off to a good start, and then we really got it going in the third quarter," said Indiana coach Nate McMillan. "Our offence was solid, we moved the ball well and we shot it well.
"We had a lot more energy than we had in our loss Monday night at Charlotte."
The Pacers were coming off three losses on a five game road trip during which they lost at Miami, San Antonio and Charlotte.
Indiana now has a two-game lead over Detroit for the No. 6 playoff spot in the Eastern Conference.
In Miami, Dion Waiters scored 24 points and Goran Dragic added 22 points and 10 assists to lead the Miami Heat to a 108-101 win over the Charlotte Hornets at AmericanAirlines Arena.
Dragic posted his fifth double-double of the season as Miami continued its hot streak, winning for the 20th time in 24 games.
The Heat have won three straight, including two wins over the defending league champion Cleveland Cavaliers.