Thailand has a strong heritage of national costume which has a history going back to the 13th century. Formal Thai costume, known in Thai as Chut thai phra ratch niyom which literally means Thai dress of royal endorsement , consists of a number of different designs that are primarily intended as national dress for formal occasions. These set of designs where conceived during the 20th century by Queen Sirikit who recognised a need for a officially decreed modern national costume which represented the tradition, culture, race, and identity of the Thai people clearly. The queen undertook research into historical royal dress, from the Sukhothai period (1238-1247), Ayutthaya Period (1350 – 1767) and Rattanakosin Period (Founded 1782), which resulted in the creation of eight official designs that were used for the queen and her aides. These dresses have since become popular in Thailand and have become an icon of Thai Traditional dress for its people and the world. These dress designs usually consist of a sinh, a blouse and a sabai. A sinh is a full length wrap around skirt with two pleated folds in the front called na nang and Sbai is a piece of fabric, often made of silk, draped diagonally over the chest and one shoulder. These two garments are often combined with a silk blouse and worn in different colours and patterns for various formal and casual occasions.