So I gave it a go and ordered my first item from Amazon Japan (mobile phone).

Summing up my experience:

11-Sep:
Ordered the item on Amazon JP (Amazon seller)

12-Sep:
Package left the carrier facility (I assume the warehouse) - JAPAN

13-Sep:
(1AM) Item was flown to Hong Kong
(8AM) Item arrived in Subang
(9AM) DHL informed me to process and submit SIRIM clearance
(12NN) Submitted the form from SIRIM website and informed SIRIM officer via WhatsApp.
(2PM) SIRIM officer approved the form and documents
(2:30PM) Paid SIRIM RM40 to get the Clearance letter
(2:30PM) Submitted the clearance letter to DHL via Email (and waiting for response)

So now, I'm waiting for DHL to acknowledge the clearance letter so they can send the parcel.
Side note for those asking why I purchased from Amazon Japan:
1. The phone model is not available in Malaysia
2. It is available in Amazon US and Amazon UK but wayyyyy more expensive. The price difference is RM1,000.