Nainggolan has long been strongly linked with a move to a bigger club.
"There are two months to go until we can do anything but we have already spoken to the management about buying players to strengthen the side," Thohir told Indonesia's TV One News.
"I like Nainggolan. Being of Indonesia origin, I would like him here, but this is the sort of decision which has to be talked through with the club first."
But Thohir insists that he is happy with Inter's current squad.
"There is a good mix of young and experienced players," he said.
"[Rodrigo] Palacio, [Andrea] Ranocchia and [Esteban] Cambiasso are great players and there is also [Yuto] Nagatomo and [Samir] Handanovic who is a great goalkeeper.
"But we will decide what to do together and Inter will still be reinforced."