Vuong Duy Bao surveys his ancestral palace, a vestige of Vietnam's marginalised Hmong ethnic minority that he says was taken from his family by local officials.The wooden structure is laden with historic markers: opium flowers carved into pillars in a nod to the region's once-booming trade, and an iron fence made with metal imported from former colonial ruler France.Built in 1903 by Bao's warlord grandfather with his opium fortune, the retired civil servant claims local authori