What a find. I did not know this existed until last month but this is a must try for anyone in Las Vegas during the fair. Prices are cheap, quality of food is exceptional, and the uniqueness of it all is unmatched.
The fair takes place on the last sunday of each month at the Chaiya Meditation Monastery. This place is out of the way and there would be zero chance that I would have known about this unless I saw the reviews on yelp.
I finally went last month and the food was delicious, as advertised. I had the pad thai (pro tip: write your name down right away for the pad thai; it takes about 20 minutes to cook and there's always a line), the satay, and dessert-type ball with I believe roti filling. The soup and papaya salad looked appetizing but there's always next month for those. All meals were $6 or less, so bring some cash and buy for enough for the next few meals during the week.
If you like thai food and you're interested in an authentic interpretation off the beaten path, then come to this fair on the last sunday of each month. There are tables to eat, or you can take the meals home. Either way, coming here is a no brainer.