Playboy Golf Lawsuit -- Babe AGREED to Butt Stunt ... Here's the Proof!

Liz Dickson knew damn well her ass would be IN PLAY when she agreed to put a tee in her butt for a golf stunt at a Playboy event in 2012 ... and TMZ Sports has obtained audio that proves it.

We broke the story ... Liz filed a lawsuit against Playboy claiming she thought comedian Kevin Klein would only be POSING with his golf club for a photo op ... and was shocked when he took a whack.

But in audio recorded on the day of the stunt, Kevin makes his intention crystal clear -- saying to Liz, "Would you allow me to place a golf ball on a tee in your butt and attempt to tee off a shot right now down this first fairway?"

Liz initially responds, "Maybe" ... and then says, "What did I get myself into?"

Moments later, she lays down on her stomach and allows a member of Klein's team to place a tee in her butt ... and seems to be 100% in on the stunt.

At one point Klein asks, "How does the golf tee feel in the butt?"
Liz responds, "Ummm ... it's poking my butt."

Klein asks, "Do you enjoy it at all?"
Liz responds, "I love it."

Eventually, Klein takes a swing and smacks Liz in the cheek. When asked if it was painful, she says "it hurt" ... but never seems to object to Kevin taking a swing in the first place.