What are the process and requirements for visa extension?

You need to file your extension to the Immigration Department Office Building (Travessa Um do Cais de Pac On, Taipa, Macao) five days before the expiry of "authorization to stay". The required docments include an application form, copy of your valid passport and document which can confirm the justification for the application. Please visit this page for details:
http://www.fsm.gov.mo/psp/eng/EoAS.html

Dear Lydia,

Thank you for your reply.

For the document that can justify my application for extension, can this be a certificate of employment from my company and would you know the estimated cost for extension?

Thanks again. :)

Yes, the certificate of employment from your company is ok for this extension. For the fee, it was MOP$100 as I remember. You can contact the office via (853) 2872 5488 directly.