Chins are naturally calm dogs but they can get unruly when they want attention or are playing. Dogs aren't like radios or a video game, you can't pull the plug or remove batteries. You have to teach them to settle down and shush. When playing with your puppy have him settle down every fifteen seconds for just a few seconds. Increase the amount of time for the break period gradually and your puppy will learn that being asked to settle down is not the end of the world or the end of the play session.

As I said, Japanese  chins aren't the most rowdy dogs but training them to calm down on command is still important. Letting your dog play indiscriminately as a puppy will only train him to play indiscriminately as an adult.