According to the paper 'Variation of Villosum in Vietnam' by Leonid Averyanov (Orchid Digest, July/August/December 2007, pp.102-106), it's on the border of Vietnam with Laos and Cambodia (below taken from article):
"These plants have remarkable flowers with pink to
purple centers of the dorsal sepal bordered with a pure
white margin (Fig. 9-12). Occasionally the pink central
area of the sepal is tinted with light green at the base
(Fig. 11). In other variants, the whole flower may be a
light dull yellowish color with a nearly white dorsal
sepal that is slightly tinted with pink, which was
observed in type specimen (Fig. 9). Another marginal
form of this taxon has the dorsal sepal with a deep pur-
ple central area margined with wide pure white border
(Fig. 12). Such plants were recently described as P.
macranthum on the basis of plants imported from east-
ern Cambodia bordering Vietnam (Z. J. Liu, S. C. Chen,
2002). Available data indicate distribution of P. villosum
var. fusco-roseum in a narrow mountain area spreading
along the Vietnamese border with Laos and Cambodia
(map 1). This rare variety is obviously a local endemic
of eastern Indochina not yet reported from other areas
of the peninsula. A few of the observed plants of this
taxon were found as lithophytes or terrestrial herbs and
were flowering from October to December."
Congrats to obtain and flower it.
