Yes you can change jobs while your PR application is in process. However, do notify ICA about this change.
You can either choose to email them at ICA_PR@ica.gov.sg or contact them physically at their offices at Immigration & Checkpoints Authority ICA Building 10 Kallang Road Singapore 208718 the following information or documents:
- An explanatory document that explains your situation and why you are considering to make the change in work.
- To provide them with a copy of your new EP /S pass
- Annex A from the new company you will be working for
- A copy of your passport biometric page