Mazzarri was appointed as head coach in May 2013, replacing Andrea Stramaccioni, who had overseen a poor 2012-13 campaign in which Inter finished ninth in Serie A.
The 52-year-old led Inter to a fifth-placed finish in his debut season in charge, with the team showing a marked improvement in performances.
Thohir - who assumed ownership of Inter last October - has now revealed that talks have taken place with Mazzarri about the possibility of extending his present deal by another 12 months to 2016.
"We had a long talk with (technical director) Piero Ausilio and Mazzarri," Thohir told reporters in Milan.
"We want to go forward with him, but haven't decided anything yet.
"He has a contract for one more year, so one plus one is two years. It will be extended to 2016."
Thohir was also coy on speculation linking Inter with a move for Rubin Kazan midfielder Yann M'Vila, adding: "Ask director Ausilio. He knows."