What 3 chords does charlie use in the birthday song?

What 3 chords does charlie use in the birthday song?
It's very easy to play,
With Ukulele, you just bar across on the third fret then put your fingers on the 4th on E and 5th on G to form the first note - Ab. The second chord you play is just moving all your fingers down a fret to a G, then for the last note, I think it's some kind of cm?
Let's call it a cm for the sake of this. But it's basically just the first chord without
your finger on the E.