No, the printing or ribs goes on the neutral wire by convention.

Of course, modifying the appliance screws up your UL certification (if you care).
The other option is that you can find at your local discount store or home center an extension cord with a switch already in it.

Here is a link that might be useful: Example of what I'm talking about

Assuming you have a polarized plug on that there blanket of yours, look closely at it. the 'blade' that goes in the wider slot is NEUTRAL. The narrower one is hot, and the one you want. Follow the wires from the plug.