I am bangladeshi pessport holder what kind of document i need to submit for Hong Kong Visa

Md, you should apply for a visitor type for HK. According to what I know, you can submit your application to Chinese embassy or consulate in Japan. The required documents are:
1. copy of your passport information page
2. finished ID1003A form affixed with a recent passport photo
3. travel itinerary
4. flight tickets and hotel reservation
5. financial proof, such as pay slips, recent six months bank statement and your employment certificate

If your application is processed by the embassy, it takes four working days. If it was sent to HK Immigration Department, it takes four to six weeks.