How to get HONG KONG visa? I am from Pakistan.

Faisal, you should understand that you need to apply for another M type if your current one is a single entry. Since you are in PRC, you can submit your application to office of HK SAR in Beijing. Here is the contact information:

Address:
No.71, Di'anmen Xidajie, Xicheng District, Beijing, China
Postal Code: 100009
Tel: (8610) 6657 2880
Fax: (8610) 6657 2821
E-mail: bjohksarbjo-hksarg.org.cn