Cài is a Chinese-language surname that derives from the name of the ancient Cai state. In 2019 it was the 38th most common surname in China, but the 9th most common in Taiwan, where it is usually romanized as "Tsai", "Tsay", or "Chai" and the 8th most common in Singapore, where it is usually romanized as "Chua", which is based on its Teochew and Hokkien pronunciation. Koreans use Chinese-derived family names and in Korean, Cai is 채 in Hangul, "Chae" in Revised Romanization, It is also a common name in Hong Kong where it is romanized as "Choy", "Choi" or "Tsoi". In Macau, it is spelled as "Choi". In Malaysia, it is romanized as "Choi" from the Cantonese pronunciation, and "Chua" or "Chuah" from the Hokkien or Teochew pronunciation. It is romanized in the Philippines as "Chua" or "Chuah", and in Thailand as "Chuo" (ฉั่ว). Moreover, it is also romanized in Cambodia as either "Chhay" or "Chhor" among people of full Chinese descent living in Cambodia and as "Tjhai", "Tjoa" or "Chua" in Indonesia.