Well for a bar/ lounge in Kowloon, I will highly suggest Sky Lounge at the Sheraton Hotel and Tower. It is located on the 17th floor, and has great view towards Victoria Harbor and Central. The price is relatively resonable too. If you are not a guest at the Sheraton, there will be a minimum charge of HKD 118.00 ~ USD 15.00 per head after 8pm.

The Oyster bar is just next to the sky lounge, but I personally prefer the seating at the lounge because the view is better.