Luckily you'll be in the best airport on Earth. A few years ago I had a tight connection (45 minutes) in Changi. My incoming flight was 40 minutes late and I eventually had 3 minutes (!!) to change terminals. Luckily on carry-on only. By running, and luck with trains and gates, I made it. On the other hand, if you have to spend hours in a terminal, there's no better place than Changi. They do a great job there.