It hasn't been reported from Vietnam as far as I know, and it was discovered fairly recently (1990). It comes from a restricted and remote mountainous area in Southern China. Its range should overlap with hirsutisimum. The elevation is pretty high, and it may get some warmish summer temps, but otherwise it stays coolish most of the year. I think the summer is its big monsoon time of year.
Its been found both terrestrially and epiphytically. The geology in the area is old volcanic so its not a high pH plant by any means.
Given the relatively recent discovery seedlings didn't become very easy to find untill about 2000, and divisions were going for some pretty big $$. It seems like the 1st generation plants are starting to realy come in to there own now.