As a local, this is by far the best Thai food in Vegas. We've tried it all and will always choose Lotus of Siam (even though it take about 25 minutes to drive for us).
Must try:
Garlic prawns
Crispy duck with drunken noodles
Tom Kah Kai soup (made with coconut milk)
Thai iced tea is amazing!
Reason for not giving 5 stars?
The front entrance is so tiny and it's always packed with people waiting for a table. There is a very small desk for the hostess. On most occasions the hostesses are overwhelmed with the number of guests and the crowd of people. They can be a bit rude and flustered. I would love to see this restaurant open a new location that is bigger and can compadre more people. Or a second location in the west, Summerlin area.
We rarely dine-in anymore because reservations are booked weeks in advanced. Also, a reservation time doesn't mean you'll be seat at that time. Sometimes another 30 minute wait past your reservation time.
We do take-out, and that is more timely. Just not great since it's 25 minutes to get the food back home. We have actually ordered take-out and sat in the parking lot and ate. It was way faster than trying to dine-in.