Kourtney Kardashian — Frowny Faced Scott Disick Front and Center for Birthday Bash (PHOTOS)

Kourtney Kardashian celebrated her 36 birthday Saturday night in Vegas with hubby Scott Disick … and he looks less than enthused.

The bash was thrown at 1OAK.  There was a pretty big crowd, sans all the other Kardashians.  Kim’s at home in L.A., Kylie’s at Coachella with Tyga and Kendall.

Khloe was busy Saturday night throwing a jamboree for her new group messaging app…