A drunkard is the kind of person who would poop two times under a tree before using a machine toilet. There’s a perfectly good outhouse with a machine toilet right there, but this drunkard is so drunk that he decides to poop under the tree instead. And not only does he poop once, he poops twice.
Oh, I see – the door to the outhouse with the machine toilet is locked, and the drunkard doesn’t have the key (き). If he had a machine like a jackhammer, or a circular saw, or some other heavy duty machine, he might be able to get in without a key, but since he has none of those or a key, he’s reduced to pooping under the tree instead.