Kanye West's new song says he's got "sick thoughts" ... and some of them involve all 4 of his sisters-in-law.
Ye released a brand new track Saturday morning on Twitter -- "XTCY" -- and along with obvious lyrics about ecstasy ... there's a very interesting line about wanting to bang Kim's sisters -- Kourtney, Khloe, Kendall and Kylie.
West raps ... "You got sick thoughts? I got more of ’em / You got a sister-in-law you would smash? I got four of them." Then he says they need a bigger hot tub.
He's yet to reply to the offer ... but now we have an idea of who he might be looking for at the casting call.