His study of medicines was, after a few years, replaced by a certificate of LO-drawing, succeeded by jobs as a drawing teacher. The security of a fixed income gave him the freedom for painting, painting in watercolours, drawing, etching, lithographing, modelling and illustrating.
He preferred to work close to nature: landscapes, barns, chambered tombs, sand-drifts and all of this in the Assen surroundings.
Kray was co-founder of the society “De Drentse Schilder”.