During some periods Bronze in much of Laos and far northern Thailand was at least partly alloyed with tin from Gejiu in Yunnan to the north. In terms of logist

During some periods Bronze in much of Laos and far northern Thailand was at least partly alloyed with tin from Gejiu in Yunnan to the north. In terms of logistics: geologically, most tin in northern Thailand / southern Laos is much further west along the Myanmar border or in deep mountains on the Laos/Vietnamese border which (either requiring a long overland journey or an upriver trip toward Ban Chiang / Vientiane) is a lot harder to access than just floating down the Mekong from Yunnan. In terms of supporting archaeology: Dong Son bronze drums. https://en.wikipedia.org/wiki/File:Dong_Son_bronze_drums.JPG https://en.wikipedia.org/wiki/File:Dong_Son_bronze_drums.JPG Note the density of findings directly downstream of Gejiu in the Red River valley which flows to Co Loa / modern Hanoi.