Joke - must read then you catch the joke

Ah beng was walking along his work area one day and saw his fren Ah mute
Ah mute can't speak so he needs to use sign language to communicate.
Ah mute signal why Ah Beng isn't at work.

Ah beng than look around and gathered some leaves under the tree and stand on them.
He look at Ah Mute and pointed down at the leaves.
Ah Mute is now confused..

Later Ah Sian pass by and saw Ah Beng standing on the leaves.
Ah mute than signal Ah Sian on what is Ah Beng trying to say..

Ah sian than type down in his handphone and show it to Ah Mute.
"Aiyo so simple, Ah Beng Is On Leave!"