Thompson, who missed out on the sole British Laser place at London 2012 to Olympic champion from Beijing 2008 Paul Goodison, is competing in his sixth regatta in the class this year in France.
He arrived in La Rochelle having finished fourth at the European Championships in August and third at the test event for next year's ISAF Sailing World Championships in Santander last month.
After four races at the fifth and final EUROSAF Champions Sailing Cup regatta, three-time world medallist Thompson, who sailed the Laser just once in 2012, held the lead.
And the 27-year-old admits he is back up to full speed after his 2012 break and fully focussed on delivering once more at the World Championships in Oman next month.
"Fourth at the Europeans was a frustrating result if I am honest. But now here in La Rochelle I'm feeling good. I'm fired up. This is a really good warm up for the Laser worlds," said Thompson.
"At the beginning of the season, I was a little bit slow at Palma and Hyeres. The long break affected me more than I thought it would.
"It was good to be back up to speed at the Euros fighting for the win but it was frustrating to all finish so close on points with me at the back of the group."