Thanks for your response and sharing your experience with me. Do you have any idea based on your experience when they are using snail mail or email instead? The reason behind that is I am going back to my country and I am worried about postal failure that I am sure it is seriously painful to miss any further request by visa office , hence the best option for me is using email service to communicate with visa office. If you have any experience regarding this matter please let me know.
Regarding Courier, I am quite sure that DHL cover the service of submitting passport to the SG VO and collecting it from them and giving back to you, but you have to live in Kulala Lumpur or have a correspondence address in KL. I asked this from a DHL service point. In the other cities of Malaysia, DHL just submitting documents such as passport to the VO, not collecting them. Which city of Malaysia do you live? In my opinion, it might be another courier companies to do the same job. IF you find out anything regarding this matter please let me know as I will faced with the same problem.
Finally, Have you recently your ECAS? Is there any new line in your ECAS to show the application package sent by KL VO is received by SG VO. For me, there is nothing new in my ECAS.
Cheers