I am a little confused with a transitive and intransitive verb form.
Can someone help me with this, please?
Laugh is used as a transitive verb as the link shows:
To affect or influence by laughter: laughed the speaker off the stage; laughed the proposal down.
To say with a laugh: He laughed his delight at the victory.
If you consider "laugh" as an intransitive verb, it cannot have an object, "your head", there. "Laugh your head off (your body)" is the same construction as the example in No. 1.