I'd give the food 3 stars. In my opinion, Penn's is nothing different from any other basic Thai restaurant I have been to around Las Vegas/Henderson. Good, but not spectacular. I have absolutely no idea what everyone is raving about so much on Yelp. Also, no beer or wine is offered.
For the record.... I LOVE hole-in-the-wall establishments with a dive atmosphere. And I am a million miles away from being a high-maintenance guy. HOWEVER, I'm giving this place 2 stars instead of 3 just because the interior is SO DAMN HORRIBLE!!! Cleanliness is not the problem. The problem is that apparently they take absolutely zero pride in their property. If you're not going to take pride in your business, and you have average food at best, you deserve nothing more than 2 stars.
The dining room is ancient looking. The aquarium needs cleaning. The lighting is rather dim, but not in a good way. It smells odd. I don't know what to compare this place to... A garage? A big storage closet? A mental institution? The cafeteria at a coal mine? It is an extremely awful dining atmosphere. The walk back to the restrooms literally feels like you're walking into a low budget peep show. Many Yelp reviews have negative comments regarding the atmosphere, so I wasn't expecting much. But I was certainly expecting at least slightly more.
Advice to the owners... Quit being so damn cheap! Brighten the place up a bit! Decorate with stuff that doesn't look like it comes from the thrift store! Paint! Clean/trash/or completely change your ugly aquarium. FIX THE FRONT DOOR SO IT DOESN'T SLAM EVERY TIME SOMEONE COMES AND GOES!!! Sell beer and wine! It boggles the mind that at some point in history you actually stood back and looked at your interior and said "Ready for customers!"
Advice to customers... Get carry out. Or go just up the road about a mile to Bangkok-9.