Higher intelligence, within the human range, is conducive to greater morality because subscribing to the moral rule is usually a rational and intelligent thing to do. If you act immorally you will usually be punished, because the moral rule has greater power than you do. It is intelligent to avoid punishment.
Yet this theory is flawed where it fails to regard:
1. Covert immorality - where one can be immoral whilst escaping notice and punishment.
2. The motivation behind the morality. One can act morally without themselves meaningfully caring about morality - being explicitly moral but of character amoral.
3. Intelligence beyond the human bounds. Where intelligence promotes power that supersedes the moral rule. Where this is true I would expect morality to be abandoned.