Jax Taylor and Lori Krebs Pack on the PDA at Charity Event in Las Vegas

Jax Taylor and his longtime publicist Lori Krebs' relationship is going stronger than ever ... the two were spotted packing on the PDA at a Vegas event that was near and dear to them both.

We obtained photos of Jax and Lori cozying up at the Grant a Gift Gala -- a charity event supporting families with autism -- Thursday night at Allegiant Stadium.

The pair were seen holding hands and sharing a sweet kiss ... and an eyewitness tells us they seemed very happy.

As we've told you ... Jax and Lori initially bonded in part over their shared experience of raising children with autism.

Our eyewitness tells us ... Lori became visibly teary-eyed as she listened to families sharing their experiences ... before Jax wrapped his arm around her and gave her head a smooch.

In another cute moment from the evening ... the couple couldn't contain their laughter during the live auction when Holly Madison showed off a brown mini mountain doodle. Holly was an event ambassador, and the dog ended up being auctioned off for $60k.

As you know ... the couple initially made headlines when we obtained photos of them getting close in a swimming pool during a getaway to Mexico.

Jax's ex-wife, Brittany Cartwright -- who was represented by Lori -- fired her former publicist after she was told about the steamy pics.