The upgrade continues a contract Thailand gave to Saab in 2011, the company said, and is worth nearly $84 million.
Under the award, which runs to 2015, additional sights and communications equipment will be added to the combat systems of the H.T.M.S. Naresuan and H.T.M.S Taksin.
"Saab will further strengthen its position as supplier to the Royal Thai Navy through the upgrade of the Combat System on the frigates H.T.M.S. Naresuan and H.T.M.S Taksin," said Gunilla Fransson, head of Saab's Security and Defense Solutions business unit.
"Saab is now on the navy's three major vessels and with data links to the Royal Thai Air Force's Gripen and Erieye, capabilities and resources can be used more efficiently."
Saab is the main contractor to the Thai navy, supplying its own equipment, equipment from third-party vendors and responsible for the integration of new systems.