He could have an intestinal infection of some sort or some sort of blockage in the intestine. Before you take him to the vet, keep watch on his eating habits along with his bowl movements. If his bowls are all like this for 2 or 3 days straight and he has poor eating habits then he probably should be seen. You should call the vets office and describe this to them before you take him. Most of the time they will give you free advice over the phone. If it is something that can be taken care of at home per say(different type of puppy food,or special diet for a few days for maybe an intestinal infection or upset) this will save you a lot of money.
Yes!! Especially if the poop is neon green, it means the dog has eaten rat poison. If the dog has eaten rat poison, he needs medical help immediately, even though he may not show other symptoms for a couple more days.