Don't have a guitar in my hands but according to what he's doing and a tab I found, it looks like the harmonic on the 2nd fret of the A string. The touch required to sound some of the less common harmonics can take some time to develop, if it gives you problems, I wouldn't bother. It's not really an integral part of the song.
Fun fact: My band also plays this song, but probably for different reasons (wookiee life debt)