hi Olaf,
is it possible that it's a natural hybrid with Paph. huonglanae x micranthum ?
both are found in Vietnam it's a well known fact that orchids don't recognize
country borders, neither do the minorities that cross borders in order to collect plants for their order,
they send them to their Patron sometimes in China sometimes in Hanoi.
so if they were coming from China they are Chinese if somebody ordered them in Vietnam they are Vietnamese ,
we see a lot of these cross border practice all over Asia .
many orchid species are being collected in China,
Myanmar,Laos and Cambodia they all are being shipped to Bangkok for sale therefor often identified as a Thai specie.
Cliokchi