Mongolia to deepen cooperation with US on rare earths, prime minister says, page-8

Vietnam does not have processing capacity.
Even mining skill is very basic, most are in coal mining and many mines cost hundred of millions to rehabilitate which was never factored in price. Titan mining and iron ore mining was environment disasters. Many mine cause both earthquake and landslide.
for these reasons, mining is never supported by local.

vietnam gov owned mining corp want to sell processed product to japan only if they transfer processing skill which jp does not want to, as skill can be leak to chia.
china only want to buy raw ore and process themself for similar reason.

vietnam rareearth will never fly high