speaking to the king or the queen. A male Luk Luang who does not accede to the throne would assume a new royal surname, normally reflecting his birth name (as opposed to an honorific given later). The surname can be used by his wife if she is a commoner by birth, possibly with Na Ayudhya added if she has no noble title. It is otherwise not normally used until his children (or grandchildren) first hold the title of Mom Chao, when the surname will first appear in their names. Sovereign's children Viceroy's children Sovereign's grandchildren Sovereign's nephew or niece Viceroy's grandchildren Sovereign's great-grandchildren Royal descendants More distant royal progeny, starting from the children of male Mom Chao, are considered commoners. However, these commoners have titles indicating that their ancestry can be traced back to a king. Mom Rajawongse Mom Rajawongse (หม่อมราชวงศ์, ; abbreviated in Thai as ม.ร.ว. and in English as M. R. and translated as "His/Her Excellency") is the title assumed by children of male Mom Chao M.C.(English) M.C. After first name Informally, they may be called Khun Chai (male) or Khun Ying (female) (). Holders of this title are occasionally erroneously referred to as princes or princesses in older English documents; it is now more common to use the correct title, "Mom Rajawongse". If a specific title is appended, sometimes the titular may be called His/Her Grace by proclamation of the King or a Prince-Regent, but not by a Queen-regent or any royal member sitting in the King's capacity as a Councillor-of-State. Mom Luang Mom Luang (หม่อมหลวง, abbreviated in Thai ม.ล. and sometimes in English as M. L. and translated as "The Honourable") are the last royal descendants retaining a title. Mom Luang titles are conferred on children of male Mom Rajawongse. Colloquially (although incorrectly), they are sometimes addressed as "Mom"; the correct informal address is "Khun" (). na Ayudhya In the Family Name Act, B. E. 2465, Rama VI ordered that royal descendants who do not hold any title should append "na Ayudhya" (ณ อยุธยา) to their surname to signify they are descended from a royal bloodline. Sometime spelled "Na Ayutthaya". Wife of prince Wives of princes have titles, depending on the titles on both sides. Phra Vorachaya Phra Vorachaya () is a title of the royal consort of the Crown Prince. She is elevated to Phra Chao Vorawongse Ther Phra Ong Chao. Phra ChayaPhra Chaya ()