Coconut oil doesn't cause constipation, in general. It's actually good at softening stool and stimulating the contraction and relaxation of intestinal muscles. No wonder so many people experience diarrhea symptoms after ingesting coconut oil.
That's the best evidence to prove that coconut oil helps with constipation, instead of causing one. But you must make sure to drink adequate amount of water.
This is because coconut oil requires water to make your stool soft and easy to move through the intestines. If you're dehydrated, coconut oil can't help much to stimulate your bowel movement and ease your constipation. It may still help a little as it tries to gather water in the intestines.