naradah prahasann iva
manusim iyuso gatim
Having thus seen this display of the Lord’s Yoga-maya, Narada mildly laughed and then addressed Lord Hrsikesa, who was adopting the behavior of a human being.
According to Srila Visvanatha Cakravarti, Narada fully understood the Lord’s omniscience, and thus when he saw the Lord trying to find out the mood of His ministers, moving about in disguise, Narada could not help laughing. But remembering the Lord’s supreme position, he somewhat constrained his laughter.