Karaoke, Hong Kong
If you're in Tuen Mun (NT) and want to sing karaoke there's a wonderful place called Green Box, in the evenings they have competitions, you can win everything you've ordered for free... or you can (as I did) win a few free Heiniken :D
Dress Code: Cool...
Not sure about anything in particular, but I do know that there exists a number of Karaoke bars. But Hong Kong is a big city, I'm sure there is everything you could possibly want in terms of nightlife.
This is a rather crazy suggestion. But if you have the guts, try to have fun in one of the karaokay restaurants in Mong Kok until very late at night, say 3 am in the morning.
Karaokay is not the key. The key is that when you leave the restaurant and go out on the street at 3 am in the morning, you would still see quite a number of people walking on the street. There is still traffic going on the road, with taxi, minibuses, or private cars racing through the road.
This is where you experience the ever-living ever-partying sleepless Hong Kong.
Of course, be alert, stay on the main road and just take a short walk. Then get on a taxi and hurry home (hotel).
Most of the disco and karaoke in Hong Kong are open till early morning, says 5:00am or 6:00am. You can meet people from over the world and just have fun.
Dress Code: Causal wears, of course there are some disco, especially those located in a hotel are requesting formal dressing.