Huge Caterpillar

This caterpillar is more than 4 inches in length and is as thick as my thumb!

This caterpillar was accidentally spotted when i wanted to get a cutting of pandan leaf plant for a friend. While i was moving the pandan leaves around i noticed these huge round pellets all over the pandan leaves and getting lodged between the leaves. They reminded me of caterpillar droppings so i looked up and saw that many leaves of my torch ginger had been eaten and only the main vein of the leaf remained. Then i spotted it. I have never seen any caterpillar this size before. It is slightly longer than 4 inches, is green in colour and has a whitish powdery skin. It is now in a cage with lots of leaves to chew on. I can't wait to see what kind of butterfly or moth it turns out to be.