Paph armenicacum is the one that comes immediately to mind. A lot would depend on how you construct the growing bed. Slightly elevated so the coldest air flows away at night. Wide enough, and sheltered enough that the soil in the bed doesn't cool off any quicker than the surrounding ground. There are a lot of tricks I am not familiar with, but the rock gardening people have tricks to handle plants in zones colder than their normal hardiness ranges.
If you can protect them from temperatures above 100F, Paph armeniacum, and micranthum are very cold tolerant. I once saw an in situ photo of armeniacum in the snow. I am not sure about other parvi's, I have had delenatii outside and it tolerates a lot more sun than one would expect. It might do ok. Problem is only delenatii is common enough that it would not be expensive testing them outside. Emersonii, hangianum, and micranthum, while available, can get expensive testing for frost tolerance.
Summer heat might be an issue for the cold tolerant species. If you are close enough to the coast you might be ok, but desert heat would be fatal to the mountain plants that tolerate cold.
you might test hisutissimum, esquirolei, & charlesworthii. All might come back from frosts, though the leaves will be severely damaged. Similarly tranlienianum, henryanum and maybe helenae. Though Vietnam is mostly frost free, it doesn't mean that somewhere in their evolutionary past these species haven't picked up some tolerance, or ability to come back from the roots after frost.