The former world number five saw his 2018 season wrecked by injury, but he has found form in Montpellier this week and will now face compatriot Pierre-Hugues Herbert in Sunday's decider.
Tsonga, a former world number five, is now down at 210 in the rankings after a lengthy battle with a knee injury.
The win was Tsonga's first since the fall of 2017 when he beat Diego Schwartzman in Antwerp.
A break late in the opener left Tsonga serving for the set and he maintained that momentum to go a break up in the second. That all changed in game nine when Tsonga scored a break with a return victor, moving 5-4 up and closing the opener with a hold at love for a 6-4.
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In the Sofia Open final, third seed Daniil Medvedev of Russian Federation beat Hungarian Marton Fucsovics 6-4 6-3. It was fourth title in 13 months.
Tsonga is in line for his 17th career title after beating Radu Albot of Moldova 6-1, 6-3.
He needed just 73 to defeat Herbert in straight sets, dropping just four points behind his first serve.
Herbert raced into a 4-0 lead in the first set and never let slip his advantage as he moved a win away from his first singles tour title.
Medvedev finished the job with a break to love.