I'm Singapore PR holder , can i apply visa at Singapore China embassy if my air ticket buy from Malaysia?

Yes, you can apply for China visa from China embassy in Singapore because you are a Singapore PR holders. You can try to apply multi entry visa for one year.

The requirements are:
1. completely filled out visa application form V.2011A and V.2011B. No item should be blank .

2. One recently taken 2X2 inch photo showing entire face and without a hat on. Please affix the photo to the application form.

3. Original passport with at least 2 blank visa pages and valid for at least 9 months beyond the date of application.

4. Round trip airline ticket and hotel reservation. Application for visiting family or friends should provide certificate of relationship.

5. Previous China visas on your old or new passport (if available)