Have you recently changed the brand of the litter?
Some cats are picky and will not go in the litter box if they don't like the litter.
Another reason will be the litter box being 2 dirty bit as you said its always clean.
Make sure his litter box isn't 2 close to his food and water as this might also cause him to poop away.

Only solution : Murder.

if there is the smell of another animal, especially a cat, they will do so as a way of marking territory. had this issue with trained cats, but a new apartment and they found a corner where previous tenants cats urinated. best bet is to try and remove the smell from the area, set a litter box where they are going, then slowly move it to another location. i set the box in the corner they kept using, eventually moved it elsewhere in the same room, them set it in the bathroom. took some time, about a month, but it worked.

Stress.

Cats can have multiple reasons why they don't like to use their litter boxes.
Does your cat still go in the litter box in addition to going on your dads bed?

-Dirty Litter Boxes
-Change of Litter/Location of box
-Change of Environment

How many cats/litter boxes do you currently have? Another good way to try is to get another litter box and see if he'll use it.

Thanks for all the answers!

pick cat up after she poops and put in litter box

My cat used to do this. I smacked the shit outta him every time he did it. He got the shit smacked outta him for like 2 years. Eventually he started going into the litter box again. Occasionally though I have to tap dat ass

this one time, I heard of cats pooping in a shoe, but maybe, it has more of a perception of thinking then just what it meant to do. Was the poop in the corner of the room? * dunce cap *

and was the poop, per haps right next to the toilette, what evidence of it's stinky nature is available. Key investigations of where the poop may or might be, will determine the out come, unless your clueless.