Which districts in Hong Kong is not safe to go at night?

i don't think there's a "not-so-safe" district. pickpockets can be everywhere and so are policemen. just be cautious when dealing with vendors. hong kong streets are still busy at night so it's so unlikely that you will be walking alone. hong kong is considered as one of the safest places. still, it's better not to travel alone, go with people. bad things can happen anywhere.

no worry

none

Ive lived her for over 13 years and have never felt in even remote danger in any part of hong kong at any time of the day and night.

However, there are a number of areas you would probably feel uncomfortable in after dark such as Mongkok and Shamshui Po but the reality is you will be quite safe there too.

Most areas in Hong Kong are pretty safe. People are everywhere even it is midnight. Just try to avoid taking shortcuts by walking the back alleys. Then, you should be fine. When you go to Temple Street or other places that have lots of street vendors and people, beware of your belongings and put your purse in the front. If you stay in the tourist area, you should be fine. You need to be careful if you stay in one of the hostels 'Chung Hing Building' in Tsimshatsui. You need to be very careful. I don't even recommend. There are a lot of folks from Africa who look for jobs in Hong Kong stay in Chung Hing Building. However, other hostels such as Caritas House and YMCA are very nice and affordable.

Hong Kong is one of the safest place. At night, though, I suggest to stay within the crowded area, where tourists and locals hang out. Most outer islands are quiet at night -- they are better visited during the daytime. Public parks, such as Kowloon Park, a great relaxing place to go during the day, I wouldn't recommend that at night unless you have a local friend with you. Be aware that even in crowded streets, such as Temple street, Jordan, and those in Central, when you wander off one block off the main streets, they could become awfully quiet at night. Stay on the main roads.

Hong Kong is a very safe city compared elsewhere in the world. I am not aware of any place considered unsafe knowing that visitors do not travel to unpopular districts usually. By unpopular, I mean places where there are less people in the street at night time, but they are still pretty safe. Here in Hong Kong, you can see many people still in the streets in busy districts like Causeway Bay, Central (Lan Kwai Fong) and Tsimshatsui at midnight.
Enjoy your stay in Hong Kong. You may avoid side lanes and back streets particularly when it is dark or that nobody is in sight. Then you will be very safe.

According to the US State Department,

Although there have been no terrorist incidents in Hong Kong, the Department of State reminds Americans everywhere that U.S. citizens and interests are at a heightened risk of attack by terrorists. These individuals and groups have proved that they do not distinguish between official and civilian targets. Because security awareness has been elevated within the United States, terrorists may target U.S. interests overseas. Private Americans should be aware of the potential risks when making travel plans and should remain vigilant with regard to their personal security and exercise caution. The State Department will continue to develop information about potential threats.

There have recently been cases where both local and foreign hikers have been robbed/beaten in country parks and Victoria Peak. Although no U.S. citizens have been reported among these victims, U.S. citizens should be extremely vigilant when walking in these areas and should travel in groups.

For the latest security information, Americans traveling abroad should regularly monitor the Department’s Internet web site, where the current Worldwide Caution Public Announcement, Travel Warnings and Public Announcements can be found.

Up-to-date information on safety and security can also be obtained by calling 1-888-407-4747 toll free in the U.S., or for callers outside the U.S. and Canada, a regular toll-line at 1-202-501-4444. These numbers are available from 8:00 a.m. to 8:00 p.m. Eastern Time, Monday through Friday (except U.S. federal holidays).

The Department of State urges American citizens to take responsibility for their own personal security while traveling overseas. For general information about appropriate measures travelers can take to protect themselves in an overseas environment, see the Department of State’s pamphlet A Safe Trip Abroad.