Like a reviewer said before me, the more popular Lemongrass (located in the old McDonald's building on Lee) truly pales in comparison.
Here it is not only authentic, but the menu is extraordinary in size and quality. Try the samlaw machu kati....your choice of meat with eggplant and peppers in a savory green tamarind curry. This place has the usual red, green and yellow curries, but it has both thai and cambodian sauces as well, all made by the family that runs the place. They have pad thai (excellent!) but also have many other pasta choices.
It is quiet and a good place to take a date or your family. Be adventurous....order a dish you've never tried and you will be back to do it again.