. Those who were born Mom Chao did not as a rule receive any other title but very occasionally an individual from among these may be created Phra Ong Chao. The lower grades hardly counted as royalties and frequently dropped their titles or exchange them for those attached to ordinary official positions usually filled by persons who were not royal. Many of the princes and princesses had more than one title, and alterations can be made, not only to their rank but also to the terms describing their relationship to the reigning monarch, which change from reign to reign. These ranks and titles are finely graded, revealing nuances which explain the exact rank and relationship to the king of the individual prince or princess. This hierarchy of rank and title is unique to Thailand [although a similar, but less complex system exists within the royal family of Cambodia] and is the most elaborate system of royal rank to be found in any country in the world. There are three distinct ranks of prince and princess, but even within each rank there are finer distinctions which divide the members into different sub-groups. The three main ranks are as follows:-