Any hat can be made to fold up..you just make it longer before you start any decreases. That said...do you want a hat that is knit flat and seamed or seamless and knit in the round?
Here's a couple very easy ones that are knit flat.
http://www.lionbrand.com/patterns/kw...noImages=0&r=1
http://www.lionbrand.com/patterns/90...terHat&r=1&r=1