The Plain would be a route from the pre-Khmer territory to Chinese controlled Vietnam, although I would guess most of that trade would go down the Mekong and then by sea.
If I had to make a bet it would be burial with some religious significance. I don't know what kind of beliefs these people had. IIRC, this was a time before the modern Laotians had arrived and this was a little north of the Hindu-influenced area.
28 posted on
10/26/2009 3:19:54 PM PDT by
SunkenCiv
(https://secure.freerepublic.com/donate/__Since Jan 3, 2004__Profile updated Monday, January 12, 2009)