When the green woods laugh with the voice of joy
And the dimpling stream runs laughing by
When the air does laugh with our merry wit
And the green hill laughs with the noise of it
When the meadows laugh with lively green
And the grasshopper laughs in the merry scene
When Mary and Susan and Emily
With their sweet round mouths sing "Ha, ha he!"
When the painted birds laugh in the shade
Where our table with cherries and nuts is spread
Come live, and be merry, and join with me
To sing the sweet chorus of "Ha, ha, he!"
Blake for the first time refers to the humans in this setting.  Significantly, they eat a meal  al fresco  that is not dissimilar to what birds and animals eat. 
 So the humans are, in effect, are partaking of the bounty of nature, linking with the Garden of Eden and suggesting a loving God still provides for mankind. The relaxed, joyous nature of the poem denies the biblical suggestion that man is punished by having to toil for food, instead emphasising the loving God nurturing his creations.
Laughing Song