We have worked with stingray hides. The skin is covered in dermal denticles , dentine just like teeth. The hide has one "eye" which is raised and when sanded
down appears white. The hides are not easy to sew because of the abrasive nature of the dentine. For a watchband I would imagine a soft piece of leather would be glued on the inner side. The hides are a available in a variety of colors
and not too difficult to fabricate to whatever you want, bootmakers would have the industrial sewing machines needed.

By the way, is there any certain location in Bangkok for vendors of the raw hides such as stingray, crocodile, etc? Not finished goods but hides.