is a princess, Chao Fa (HRH Princess) or Phra Ong Chao (HRH Princess) who is married to prince, at every level. She retains her own title. When referring to her as a wife of the prince, she may be called "Phra Chaya Nai (husband's name)". ChayaChaya (ชายา) is a princess or Mom Chao (HSH Princess) who is married to prince, at every level. Again, she would retain her own title. When referring to her as a wife of the prince, she may be called "Chaya Nai (husband's name)". MomMom (หม่อม), in this context, is a commoner married to a prince. She uses this title as a prefix of her name, adding na Ayudhya to her new surname; for example, Mom Srirasmi Mahidol na Ayudhya (a wife of Chao Fa Maha Vajiralongkorn, whose surname is Mahidol). If she has her own title (Mom Rajawongse or Mom Luang), she retains it. Married princesses The son of a holder of the following titles generally inherits a title one step below; a female Mom Rajawongse married to a commoner would produce a child with no title. According to the Royal Marriages Act, B. E. 2475, a princess wishing to marry to a commoner must request royal permission and abandon her royal title. For example, if princess Chao Fa, HRH Princess of Thailand, wished to marry a Mom Rajawongse commoner she would lose her royal title (Chao Fa, HRH Princess of Thailand) but retain royal style as follows: Chao Fa, HRH Princess of Thailand: Tunkramom Ying (daughter of the sovereign with the queen) Tunkramom Ying Ubolratana Rajakanya, formerly Somdet Phra Chao Luk Thoe Chao Fa Ubolratana Rajakanya Chao Fa, HRH Princess of Thailand: Somdet Ying (daughter of the sovereign with the royal consort) Phra Ong Chao, HRH Princess of Thailand: Sadet Phra Ong Ying (daughter of the sovereign with the concubine) Phra Ong Chao, HRH Princess of Thailand: Phra Ong Ying (daughter of the son of the sovereign with the queen and his royal consort) Phra Ong Chao, HH Princess of Thailand: Than Phra Ong Ying (daughter of the son of the sovereign who was elevated from Mom Chao to Phra Ong Chao) Mom Chao, HSH Princess of Thailand: Than Ying (daughter of the son of the sovereign and his consort, or great-granddaughter of the sovereign) However, Chao Fa Chulabhorn Walailak received permission from the king to keep her title when she married commoner Virayudh