Complex sentence: Srivijayan traders seems to be engaged in extensive trade and exploration, which reached coastal Borneo, the Philippines archipelago, coastal Indochina, Bay of Bengal and Indian ocean, as far as Madagascar.
Split into simpler sentences: Srivijayan traders seems to be engaged in extensive trade and exploration. Which reached as far as coastal Borneo, the Philippines archipelago, coastal Indochina, Bay of Bengal and Indian ocean, as far as Madagascar.