Thais from the Northeast section of Thailand, Issan (or Esan), consider themselves Lao, and historically this part of Thailand and Laos have very close connections reflected in the music, dress and of course the food. E-San's chef, Ting Pathammavong, was raised there, and now she blends her own variations of recipes from her traditional land.
For over 10 years, Ting worked in the kitchen of just about every Thai restaurant in Portland before a friend suggested that she and her husband, Mao, open up their own. That was over 6 years ago, and if asked about it, Mao smiles and says he still loves it, and would rather be at work than at home. He jokingly says that when he is at home, his twin daughters play with each other, leaving him nothing to do.
The adage of Thai cooking is simple: Cook with your tongue! In traditional Thai cuisine, recipes are more like guidelines, and each chef is free to deviate to compensate for a particular ingredient's flavor changes or to fit a new locale. In fact, many Thai chefs have difficulty with western cooking because in Thailand, there are no measuring cups.
Thai chefs learn to cook by watching and helping in the kitchen... by "internalizing the system" instead of by following written instructions. This is why you will find such a wide variation between restaurants.