If a pregnant woman is having stomach pains & very lightly spotting is it ok to put a cool cloth on the stomach?

Yes in general: Depending on your gestational age, you might want to call your OB provider about the pains and spotting, especially if not after recently having sex. But to answer your specific question, heat and cold generally are not able to penetrate the layers of your skin or abdomen enough to reach your baby. So cool cloth or heating pad are not actually harmful.