Thauvin struck the second from the spot nine minutes later following a handball by Mathieu Debuchy, sealing a straightforward win that put Marseille fourth on 44 points, one ahead of St Etienne.
Earlier in the afternoon, Olympique Lyonnais forward Moussa Dembele struck two second-half goals to round off a thumping 5-1 win over visitors Toulouse in their clash at the Groupama Stadium.
Memphis Depay opened the scoring for the third-placed home side after 10 minutes but the lead was short-lived as Matthieu Dossevi put Toulouse back on level terms five minutes later.
Bertrand Traore put Lyon back in front with a bizarre goal on the half-hour, whipping a left-foot effort into the danger area that goalkeeper Baptiste Reynet allowed to fly past him.
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Lyon went 3-1 up five minutes later when Nabil Fekir won a penalty which he fired home himself and Dembele's double put the icing on the cake for the hosts.
Lyon are now five points behind second-placed Lille, who won 1-0 at home to Dijon, and 22 adrift of runaway leaders Paris Saint Germain, who have 71 points.
Elsewhere, bottom side Guingamp secured a point with a scoreless draw at home to Nantes while Nice beat Strasbourg 1-0 in a game that saw Nice's Danilo and Strasbourg's Samuel Grandsir both sent off after an ugly 89th minute confrontation.
(Reporting by Phil O'Connor; Editing by Ken Ferris)
