I hold myanmar passport n working in singapore. I want to go Hong Kong for 1 week holiday.

First, prepare the documents: travel itinerary, copy of passport, the application form, a passport-style photo, financial support proof, flight tickets and hotel booking record. Next, submit the application to Chinese embassy or post it to HK immigration department directly.
Here is the address:
Receipt and Despatch Sub-unit
HK Immigration Department
2/F, Immigration Tower
7 Gloucester Road
Wan Chai, HK