Thohir has been in talks over acquiring a 70 per cent stake in the club. Inter are yet to confirm any details of the agreement, but Moratti said in an interview on the club's website that an announcement will follow shortly.
"It has all been signed," he said. "I believe there will be a press release in the next few hours."
Moratti assured fans he was putting the club in good hands even as he came to terms with handing over control.
"When you are changing something as big as this in your life, you do not yet know how it will affect you," he said. "There's a love for the thing, and also a satisfaction to think you have put it in good hands. I'm sure of that because these are very decent people with good character."
The Moratti family has had a long association with Inter, with Massimo the fourth son of Angelo Moratti, who was the president of the club during their so-called 'Golden Age' in the late 1950s and 60s.
The younger Moratti took over as president in 1995. He said he did not yet know if he would remain at the club.
The move will see Thohir expand his already considerable interests in sport. He is a part owner of the NBA's Philadelphia 76ers as well as the owner of two basketball teams in Indonesia, and is a part-owner of Major League Soccer club DC United.
Inter have a board meeting scheduled for October 28 which will be led by Moratti.
The president said he did not know whether the formalities of the takeover would be completed in time for that meeting, or whether an extraordinary meeting would be required thereafter to confirm the new board.