Hoya hypolasia is very picky about watering.  The soil wants to be slight damp to the touch and never allow it to dry out completely.  On the other hand never, ever water it too heavily, or it will drop leaves and go into a sulk very quickly.  Watering is best judged with experience, and I don’t consider this to be a Hoya for the novice grower.  It also like so many Hoyas of its type really wants to grow in a humid atmosphere.