The midfielder admits Pep Guardiola had a big influence on his decision.
Thiago told the club's official website: "On the one hand, there's the history of the club, which has been one of the best in the world for many years. On top of that, this team plays very attractive football. And I believe the arrival of Pep Guardiola will provide an additional boost.
"We've known each other for a long time and he's a coach who has placed great faith in me. I'm a huge fan of the way he likes football to be played.
"There aren't many coaches in the world with his ability. He was definitely one of the important reasons for me making the move to Munich."