Are the musical ensembles from cambodia Indonesia and myanmar similar ?explain

Yes, We can say so. It is because of the geographical origin as well as ancestral origin of all the southeastern countries of Asia. You might have seen them adjacent to each other.

Let me give an example. Cambodian court music is somewhat similar to that of Java, Indonesia. It features choruses with large orchestras based on stuck keys and gongs. Similarly, there are several more such similarities in their instruments and way of musical celebrations.