/cast [noform] Moonkin Form

or

/cast !Moonkin Form

The issue with the first is that it will count travel form as a form and not shift you immediately... the 2nd can be spammed but it could eat a couple of GCDs and waste a little mana as it will do a shift from Moonkin -> Moonkin but I find this much more helpful when clearing movement impairing effects instead of going Moonkin -> caster -> Moonkin.

I basically have the first in front of my castsequence macro to make sure I'm in form, and the 2nd shared with my totem drop button for my shams.