I have seen farmeri growing in situ in my home state of Kedah, namely in the Langkawi Islands and in the Muda Forest Reserve.
and as Zainal mentioned they grow on the trees and rocks too. The places where they grow are quite exposed and receive a large amount of sunlight. Indeed on a small hillock in the Pedu area of the Muda Forest Reserve, we have 2 varieties of farmeri growing on a very huge boulder, completely exposed to the sun! As to whether they need a dry period ....... well, we have at least 3 months of dry weather from Dec to Feb. I grow my farmeri together with all my other orchids and water them twice a day (unless it rains) and the farmeri seem to be growing well and bloom every season without fail. I guess they are very adaptable.