OP
you need to read this taken out from ICA website
Documents Required
For All SPRs
Completed Form 6 . Download Notes - REP. You will require Adobe Acrobat Reader to read and print the form. You may also obtain the form from the Permanent Resident Services Centre.
Permanent Resident Services Centre
5th Storey, ICA Building
10 Kallang Road
(Next to Lavender MRT station)
Singapore 208718
Singapore blue identity card/Identity card for National Service personnel
Valid travel document
Latest REP, if any
Additional Documents Required for SPRs under the Professionals/Technical Personnel and Skilled Workers (PTS) Scheme
If you are an employee
A letter (issued not more than one month ago) from the employer addressed to the Controller of Immigration, stating the date of employment, position held and monthly salary
Statement from the CPF Board showing the CPF Contribution History for the last 12 months
Income Tax Notice of Assessment for the last 3 years.
http://www.ica.gov.sg/page.aspx?pageid=152&secid=150