Tom Kha Kai  is a spicy and sour hot soup with coconut milk in Thai. A mild, tamer twist on Tom Yum, this iconic soup infuses fiery chilies, thinly sliced young galangal, crushed shallots, stalks of lemongrass and tender strips of chicken. However unlike its more watery cousin, lashings of coconut milk soften its spicy blow.

Topped off with fresh lime leaves, it’s a sweet-smelling concoction, both creamy and compelling.

In a Thai-style tom kha kai, dill weed is not used, whereas in a Lao-style tom kha kai, dill weed  is used. Dill weed is a common herb which is used in Lao cuisine. The Thais’ answer to dill weed in Thai tom kha is coriander or cilantro .There are other versions of tom kha kai made with seafood, mushrooms , pork  and tofu.

In the late 19th century, tom kha was not a soup. it was a dish of chicken or duck simmered in a light coconut broth with a generous amount of galangal. It was then served with a basic roasted chili jam as a dipping relish.

Read more at: http://www.bangkok.com/food-top10.htm?cid=ch:OTH:001