@ Ogedai "The Burmese and Khmer were periodically in competition with the Tai kingdoms." Most of thes kingdoms waxed and waned depending on the power and influence of particular kings; frontiers were very fluid.
@ Sword "in that area you have a whole bunch of civs, like in Europe. Nam Viet, Burma, Khmer, Java and Thailand " India is approximately the same geographical size as Europe and more culturally diverse. And try overlaying Indonesia on a map of the USA.
The Bronze Age probably started along the Irrawady (sp?); its one of the few places on earth where copper and tin deposits are close enough together for a single kingdom to control them easily. And let's see: Cotton, Silk, Rice, Domesticated Poultry, Open Sea Navigation, the world's longest poem, two major world religions, early urban centers, Zero, "arabic" numerals, depth psychology, ... yep, beats the "Cradle of Civilization" hands down.