If I recall correctly you don't actually need cores for Malaya.
Exactly.
I've already pointed out the method in another thread so it's not really a secret.
You need to control two out of three malay regions -- easily done.
You need to discover West Java -- there is natural spread from Majipahit, if you do it right.
You need colonists -- take "Colonial Venture" (and the Malacca CoT)
It's really the colonist aspect and spread luck that determines formation time. This record was obviously a little "reload for lucky spread"-oriented, but I did it by 1430 in an MP game without this detail and it usually happens before then. Might I add that the West Java provinces do not have to be "full size."
---> Then Asia is yours. ; )