The native of Whistler, B.C., recorded her third straight victory Saturday, the first time she's ever captured three consecutive events. In 2012, she registered back-to-back victories.
Anna Holmlund of Sweden finished second, ahead of France's Ophelie David.
Thompson said she enjoyed competing on the French course.
"This course really plays to my strengths with big features that need to be pressed as well as fast straight sections that allow me to glide," she said. "Overall the course is a lot of fun as well as super competitive and that makes for great racing for both men and women."
Vancouver's Georgia Simmerling was third in her semifinal heat and just missed advancing to the final as the top two finishers advanced.
Calgary's Brady Leman finished third in the men's event, his best effort since a third-place effort in March 2014.
Leman finished second in his semifinal head to advance to the final, where he was edged out by Switzerland's Marc Bischofberger and France's Jonathan Midol.
"The final was a battle from start to finish," said Leman. "When a race like that comes down to just a reach it is unbelievable, but it all counts!"