Panel 1
Waiter: "Sir, I’d like to ask you to take off your cap in this restaurant."
Smurf: "Take off my cap? You’re not asking me to take off my pants, are you?!"
Panel 2
Waiter: "That’s not the same."
Smurf: "That is the same."
Panel 3
Cook (to waiter): "Let him put his cap back on."
Waiter: "That’s maybe better."
The smurf's being asked to remove his hat since wearing it in a restaurant is considered impolite. When being pressed the smurf says 'I don't ask you to remove your pants'. When it's revealed the smurfs genitals are under his hat Dirkjan's mate says 'maybe we should let hem keep his hat on'.