Trackhouse rider Ai Ogura and Martin's teammate Marco Bezzecchi finished second and third, respectively, in the 10-lap sprint, while Ducati rider Marc Marquez's championship hopes suffered a setback when he started sixth but finished ninth.
The victory moved polesitter Martin to 220 points in the standings, with Ogura in second place, 17 points behind the Spaniard.
Marquez was struggling by the end of the race due to tyre wear and secured the last point just as the chasing pack caught up with him near the finish line.