This paper aims to study the meanings of the heroine’s horse-faced mask in the story of Kaeo Na Ma, The two versions investigated here are the version composed by Prince Phuwanetnarinrit and that of the Ratcharoen written by Nai But and influenced by the former version. Since Prince Phuwanetnarinrit’s version firstly indicates that the heroine’s horse face can be moved, it is considered as a mask in this paper. Like other masks in Khon or masked drama, the horse face controls the behavior and personality of the wearer. This horse face not only signifies the heroine’s tomboyish manners as stated in other studies, but also communicates various hidden meanings complying with her other characteristics and behaviors. Five meanings are discussed here including the heroine’s unrefined behavior, self hiding, protective gear, ugliness and peculiarity, and masculinity. All of these meanings also exist in Thai sayings, in some literary works, and in the context of the story itself. This horse-faced mask enables the heroine to present her ‘self’ in three different guises and personalities, namely the character of a comedian in the figure of Nang Kaeo; a heroine in the figure of Nang Mani; and a hero in the figure of Manop, an unnamed man. Compared to the abstract meaning of wearing many masks at the same time, Nang Kaeo is very efficient in performing several duties at the same time. She takes good care of her family and society. It can be said that she is the first warrior heroine in Thai literature and has much influence on other warrior heroines in Thai tales. Nonetheless, as beauty is a typical this story has to remove Nang Kaeo’s horse face before appointing her his queen- the act that proves the denial of an ugly heroine in Thai tales.