Trying to tell the difference between Asils, Thais, Shamos, etc can be very tricky. Its often about like trying to tell the difference between an English, American, and Irish game; even an expert can get it wrong from time to time. To many the names could be interchangeable but its not until you get into to the subtle details that you find the distinctions. To further the confusion there are subtle differences in groups within each breed as well. Some Thais may look more like an Asil, some Asil may look more like a Thai. Generally speaking Thais to my knowledge are a taller stationed, somewhat lankier bird when compared to the Asil. Weights are also a factor. Part of why they look similar has to do with ancient ancestors and similar gene pools, the other part is that when bred for a specific "job" several breeds from different areas can come to look like one another. Consider dogs - a Golden Retriver, and Chesapeake Bay, a Labrador, and crosses of these. All similar, all developed in their own time (some with influence genetically from others) and in the end they all do the same job and have a very similar build.