Dear Dave,
In fact Saint David of Thessaloniki was not an stylite but a dendrite (δενδρίτης from the Greek word δένδρον=tree)from Messopotamia (Irak). He become a monk in Thessaloniki, at Latomou Monastery, a quite important monastery for two reasons a) it has got in the apse of the katholikon a protochristian mosaic with an image of an adolescent Jesus Christ sorrounded by the tetramorfos (Orfic Christ) and 2) becouse, apart from Saint David, Saint Joseph the Hymnografer also was monk in that monastery for some period, when he left Sicily because of the Arab conquerors. The relics of your patron saint are currently at Saint Theodoras Monastery in the Thesaloniki. Today the relics of Saint David will be againt at Latomou Monastery where an All Night Vigil will be celebrated. May Saint David bless you and all your family and friends always.