If your student visa will expire in 4 weeks, you are required to apply for 'Extension of Stay' at the Immigration Department. For details, please visit the website of the Immigration Department at:
Non-mainland students:
https://www.immd.gov.hk/eng/services/visas/extension_of_stay.html#non
Mainland students:
https://www.immd.gov.hk/eng/services/visas/extension_of_stay.html#mainland
If you need to re-apply your student visa, please refer to the application procedures in SharePoint:
https://mycuhk.sharepoint.com/sites/Central.OSA.LCES/osa.lces/SitePages/Visa.aspx
The completed application form and other required documents should be submitted to the Learning and Cultural Enhancement Section, Office of Student Affairs for further processing.
For both applications, you are required to submit a certifying letter issued within the last 2 months by the Registration and Examinations Section. You may apply online at:
https://rgsntl.rgs.cuhk.edu.hk/rws_prd_life/rws_appl/appf_crtltr_ug.asp.