If Thailand is like China, they were English names chosen by kids in English class. Not their real nicknames, just the names they use when speaking and writing English, and chosen with all the tact and creativity of a middle schooler without much knowledge about standard English names in the west. Also, since Chinese names often have meaning, they often go for English names with meaning as well (although unrelated to their Chinese name).

A famous English name in expat in China circles is Rainy.