Tristan, Ben Show Up at Same Club

So, the ex-boyfriends of Khloe Kardashian and Kendall Jenner walk into a bar, but Kylie Jenner's already there -- there's no punchline here, just a weird night in West Hollywood.

Kylie was hanging out inside Delilah nightclub well after midnight Thursday morning when NBA stars Tristan Thompson and Ben Simmons rolled in shortly before 2 AM ... aka closing time.

They didn't stay too long -- 5 minutes later, Simmons bolted ... maybe because he saw Kylie, maybe because it was closing? A few minutes later, Kylie and Tristan took off too ... separately, mind you.

Unclear if Kylie had any interaction with Kendall and Khloe's ex-BFs, but as they say ... Hollywood's a one-horse town.

As you know ...…