Ms.Jenny, you don't need to make online appointment if you apply for Hong Kong visa. Please read the below information carefully. Only ordinary passport holders applying for Chinese visa at the embassy need to make an appointment.

From 14th May 2010, 12:00 PM, the Chinese Embassy in Singapore will stop accepting all walk-in applications of Chinese Ordinary Visa, and accept only applications with online appointment. Kindly make an appointment. Please bring along the receipt of appointment to Chinese Embassy to process your Visa.
Please note that applicants holding Diplomatic, Service or Official passport, or who are qualified to apply for the Chinese Diplomatic, Service, or Courtesy visa , or who apply for Hong Kong visa/ entry permit, should still submit the application directly to the Chinese Embassy.