นางสาว

From นาง (naang, “woman; female title”) +‎ สาว (sǎao, “young female adult; young”).

นางสาว • (naang-sǎao)

1. (law) a formal title which an unmarried woman over 15 years of age is required to use, and which a married woman, irrespective of the age, may use instead of the title นาง (naang). Abbreviation: น.ส. (nɔɔ-sɔ̌ɔ)
2. similar title, as miss, etc.
3. (chiefly in compounds) maiden; miss; young woman.
   • นางสาวไทย

     naang-sǎao tai

     Miss Thailand (beauty pageant title)

• A woman under 15 years of age is required to use the title เด็กหญิง (dèk-yǐng). A married woman, irrespective of the age, is required to use either the present title or the title นาง (naang).
• A man under 15 years of age is required to use the title เด็กชาย (dèk-chaai), and that over 15 years of age is required to use the title นาย (naai).