Santhals maintained a distinct features and culture and they live seclusive life. They are no way related to Bengalis. Santhals look more like Low Caste Hindus. At least my eye sight say so.
Although Gias uddin guy looks more Indian than anything. Even you confused him with another Indian guy! I don't think he looks Arab/Turk/Persian or any of those races which you guys look up to.