As someone with a strong interest in southeast Asia, I can say that it is uniquely poorly served by world history books. Andrew Marr's loudly-trumpeted book - probably the most popular world history of the past few years, and one with its own BBC adaptation - presented itself as comprehensive, but included no references at all to pre-modern southeast Asia. Even Angkor is absent, which is just... there are no words. Given that southeast Asia actually has more people than the whole of Europe including the entire population of Russia, at over 600,000,000 inhabitants, this is a bit of an oversight. And it's a common trend. It's not that Marr is a bigot who hates southeast Asians (well, I assume that's not the case), but rather that it is considered acceptable to skip southeast Asia and concentrate on India, China, and - obviously! - Europe. It seems to be thought of as a place for tourism and cuisine, not serious academic understanding.
This is hardly the only example of neglect. The southeast Asian history/politics section of Blackwell's on Broad Street in Oxford is behind a bloody great pillar with about thirty centimetres of clearance either side. It's difficult to casually browse for southeast Asian history books, and there aren't many of them in any case. I assume they're there because they aren't in high demand, unlike the books on China, Japan, and so on, but it's not exactly a set-up guaranteed to drive demand, is it?
So here's the truth: Southeast Asia is an important place. It has a large population, its products were sought for centuries - even millennia - in Asia, Africa, and Europe, and it was the main conduit, and its people probably the prime instigators, of pre-modern Indian Ocean trade. Bananas are in Africa because of southeast Asians, as are Asian rice, southeast Asian yams (as opposed to African ones), and Austronesian loanwords. Chinese people are in Singapore, Malaysia, Indonesia, Thailand, and elsewhere primarily because of the commerce southeast Asian people generated.
Cloves, which came only from Maluku in eastern Indonesia, have been found in the pot of an eighteenth-century BCE Syrian merchant from the city of Terqa. His name was Puzurum, and he was a middle class fellow, hardly a magnate. How did he acquire cloves from so far away at such an extremely early time depth? The fact that such a low-level merchant had come into possession of these things implies that they were relatively common. How is that possible? Does it tell us that traders from Indonesia were travelling to Mesopotamia in the Bronze Age?
That seems like the only reasonable explanation, given the available evidence. And that points to the genesis of Indian Ocean trade being in southeast Asia, not India, China, Africa, the Arab world, or elsewhere. Most popular accounts, seemingly out of habit, ascribe the origins and development of Indian Ocean trade to 'Arabs', which is a little odd given that much of Arabic nautical terminology is in any case derived from Persian. But it seems that southeast Asians - Kunlunren in Chinese accounts of Indian Ocean shipping, which are almost unanimous in their claims that ships and crews on the Ocean were southeast Asians - were the prime movers, which is hardly surprising given the strong nautical traditions of Austronesian speakers and the seaworthiness of their outrigger-ed craft.
And here's the thing about Indian Ocean trade: it's why Columbus, Bartolomew Dias, and da Gama sailed. It's what they were trying to get to; they wanted access to the trade in gold, spices, slaves, precious stones, fragrances, and everything else they could only find in Europe at extortionate prices and through Muslim traders. They wanted a slice of the Indian Ocean pie, and that pie was at least as much a southeast Asian creation as it was anyone else's.
Moreover, the fabled wealth of the east came from accounts of southeast Asian cities and spices as well as Indian and Chinese ones. Southeast Asian traders brought sandalwood from Timor to ancient India, China, and Europe, provided the earliest historical mention of New Guinea, and developed a tradition of large, yet diffuse, urban centres focused on international trade. Many were wealthy and literate. They drew on traditions from across Afro-Eurasia and produced an artistic output in stone, story, and song that is just as unfairly neglected as their role in the history of commerce. The Periplus Maris Erythraei, Ptolemy's Geography, the accounts of Odoric of Pordenone and Marco Polo - they were all inspired, at least in part, by southeast Asian wealth, and they in turn inspired Columbus and da Gama and all the others. There's a strong argument that their voyages were a key determinant of the modern world and the disproportionate wealth of Europeans. The genesis of all of it, from cloves in ancient Syria to Roman coins and Chinese jades in ancient Vietnam, from Polo's discussion of sago processing to the creation of the Portuguese empire, is to be found in the adventurous sea-borne lives of southeast Asian traders and their societies back home.
The average summary of world history fails to take proper account of the lives of the ancestors of the 610,000,000 people of southeast Asia, and in doing so it fails to take proper account of the development of human civilization. I find this to be a terrible thing and one that should be amended.