I am Vietnamese. I am studying in Canada. In this December I will fly from Canada to Vietnam. In my fight schedule, I must transit in Amsterdam for 1.5 hours and then in Paris for 3 hours. I wonder if I need a Schengen Visa to flight from Amsterdam to Paris in my schedule?
Yes, a flight between two Schengen countries is considered a domestic flight, so you will need to pass border control in order to board your flight from Amsterdam to Paris.
You definitely don't need a visa to connect in Amsterdam, as their Schipol is a "single terminal airport". I.e. when you arrive from Canada, you will not cross the borders waiting for your plane to Paris. In Paris everything depends on the terminals usage: if you depart from a different terminal than arrive from, then there is a chance you would have to cross the borders. This would not be a definitive blocker yet: even in such a circumstance, borders officer may grant you a 24-hrs transit visa so you are able to continue your flight. However, the best way to do it is to check with your airline.