Terence: Kai, what are you doing now?
Kai: I'm watching TV!
Terence: What's on TV?
Kai: It's a turtle!
Terence: What colour is it?
Kai: It is black!
Terence: Can I talk to Ah-ma (grandma) now?
Kai: OK! Ah-ma!
(*In parent-speak: Normal, almost like an adult.)
# # #
And it seems that he knows when to make a noun a plural or a singular ("oranges" vs "orange"), as well as form possessive nouns ("mummy's car").
But he's still using the third-person when referring to himself, rather than first-person. I've been explaining when he uses "I" rather than "Kai". Sometimes he remembers, sometimes he forgets.
Anyway, we are proud to declare that our son speaks perfect English. (At least for now. I'm convinced that will change once he goes to primary school, where he'd pick up all sort of bad habits.)
It really isn't rocket science. Just make sure you speak well in your daily interaction with him and everyone.
Now I just need him to pick up more Chinese words and phrases.