Is there a night bus from Causeway Bay to Kwai Chung since working till around 12 am?

Hi, firstly, both the places you mentioned cover a large area. It is hard to tell you the exact direstion. Thus hereunder is a geneal direction:
No direct night bus can take your for the journey, but you can still reach where you want to go by transfer. Walk from Causeway Bay to Yee Wo Street, and you can catch bus no. N122 to Mei Foo Bus Terminal. There you can transfer to bus no. N260 or N269 and get off at Kuai Chung Interchange Station. The buses all are in service during dawn, so no need to worry about the schedule.