Hello,
My paternal grandfather was an ethnic Chinese (from the Canton region) born in Saigon, Vietnam. His surname is rendered Thái (Thai, with acute accent over the "a") in Vietnamese. I have asked several Cantonese speakers to write the Chinese character for this name, and they have all written the character which means "peace", "grand" or "Thai" (as in Thailand). As far as I know, this surname is unique and doesn't have any associated meaning. Can anyone shed further light?