In Hebrew usage and Israel, Chai means life.
'Chai' isn't a word in Japanese. If you mean 'cha' it means 'tea'. It might be you mean it as a name, written 茶衣 /chai/.
It means "Alive".
If I'm translating correctly, it means Which person? or Which person is it? something along those lines :) (that's only if 'koon' is prounounced as 'kohn')
"Life", "living", or "alive", depending on the context.