Miley Cyrus -- Next Stop ... Porn!!

One wedgie is not enough for Miley Cyrus -- instead she flaunted TWO of 'em ... in the back and the front during the latest stop on her world tour.

Miley yanked her catsuit up way high on stage in Madrid, and bent over to show the front row more crotch than the average lap dancer.

If her outfit wasn't already covered with money ... surely everyone in the crowd would have thrown singles. Or $20s.

And the countdown to Miley's sex tape continues.