Prior to the arrival of the Europeans on the scene, the island chains in South-East Asia, specifically in the area of today's Indonesia, Philippines and neighbouring states, housed a varied and conglomerate mix of mostly Muslim and Hindu nations and city-states. Most notably, these were the remains of the once-powerful Srivijaya Empire and the vassals and subjects of the Majapahit Empire. The people on the islands had extensive trade connections with the Muslim world, India and (until the beginning of the Ming Dynasty's isolationist policies) China.
However, the Europeans didn't establish any presence in the area until later in the 16th century, so European sources for the time before are scarce to non-existent, and later sources mostly concern themselves with the European exploits in the region. Consequently, Emma Helen Blair's otherwise excellent "The Philippine Islands, 1493-1803" only starts in the year 1493.
Now, for a practical application of this knowledge, I'm researching this subject in order to create a better, more true to the real history, map of this area for the game Europa Universalis III, which starts in the year 1399 (with the current expansion).
So the question would be, what were the demographics and economics of South-East Asian islands around year 1400, give or take a generation or two? In particular, the interesting part (as it pertains to this question) is how many people lived there, especially in the Majapahit Empire, but also, how did they live, and what did they trade with each other?
I'd imagine there should be a wealth of Islamic sources, and likely some Indian and Chinese as well, but finding any of them or alternatively Western ones which translate and synthesize them is a task I have failed at so far.