Out of the three orchid rich regions of the world, namely, Equatorial regions in South America and Africa as well as the tropical rain forests of South Asia, South Asia is home to a large number of orchid species. This vast variety of orchids includes those strange and unique features. Many of these orchids are quite delicate; while others are more adaptable or hardy. I will list some of which I found quite hardy.
Out of all the orchids that I have grown, Phaius tankervilleae is the hardiest. Though in wild it grows in very humid environments, still I found that it can survive dry climatic conditions also.
Other hardy species are: Acampe papillosa, Aerides fieldingii, Aerides multiflora, Aerides rosea, Arundina graminifolia, Bulbophyllum crassipes, Cymbidium aloifolium, Luisia trichoriza, Pholidota imbricata, Papilionanthe teres, Rhynchostylis retusa, Smitinandia micrantha.
Orchid species which are comparatively less hardy and require somewhat more care are: Acampe ochraceae, Aerides odorata, Agrostophyllum khasianum, Bulbophyllum andersonii, B. gutulatum, B. listeria, B. ornatissimum, Calanthe tricarinata, Coelogyne cristata, C. flaccida, C. flavida, C. ovalis, Cleisostoma aspersum, C. racemiferum, C. subulatum, Cymbidium eburneum, C. ensifolium, C. iridioides, C. pendulum, Dendrobium anceps, D. aphyllum. D. bicameratum, D. chrysotoxum, D. crepidatum, D. cumulatum, D. densiflorum, D. farmer, D. fimbriatum, D. formosum, D. jenkinsii, D. lindleyi, D.moschatum, D. nobile, D. transparens, Flickingeria macraei, Gastrochilus inconspicuous, Herminium lanceum, Panisea uniflora. For these orchids you need to keep humidity levels on the higher side (< 75%). Orchids like Cleisostoma subulatum grow in deeply shaded humid areas, so keep them away from direct sun light.
Some orchids are so delicate that changing environmental conditions have had a very drastic effect on them. Many of these are struggling to survive even in wild. Consequently, have either become rare or have completely vanished from that area. These orchids are: Ascocentrum ampullaceum, Dendrobium aduncum, Gastrochilus calceolaris, G. dasypogon, Goodyera biflora, G. repens, Liparis bistriata , L. longipes, L. plantaginea, Luisia brachystachs, Micropera manii, Oberonia iridifolia, O. pachyphylla, Otochilus alba, O. fuscus, Pholidota griffithii, Pleione maculate, Phalaenopisis mannii, P. parishii, Pterocerus suaveolus, Renanthera imshootiana, Thelasis pgymea, Thunia alba, Vanda cristata. These require specific care. When attempting to grow orchids from this list, you will have to pay more attention on the growth needs.
Let me point out here that if an orchid becomes rare or extinct in wild, it does not categorise it as delicate. Sometimes due to a variety of reasons, orchids are collected blindly from wild; leaving behind dwindling populations. Take for instance, Phaius tankervilleae. I found this orchid to be highly adaptable, but unfortunately, in wild it is quite rare.