He doesn't go back. The movie is a continuation. The bit at the start where he's there with his girlfriend and she turns undead and he kills her with the shovel and buries her in the backyard and then the camera flies into his face? Y'know, all the stuff that HAPPENS IN THE FIRST MOVIE? Same girlfriend (Linda), same necklace, same scenes. That's a RECAP. It's a RECAP of the first film, with all the characters who aren't Ash and his gf cut out for simplicity's sake.
If you remember, the first film ends with Ash, in the morning after, limping out of the cabin but then suddenly the Evil flies up into him and we cut to black with the assumption that he too has been possessed. If you notice, there is an IDENTICAL scene near the start of this film, after the stuff with him and his girlfriend.
So the plot of the new movie picks up with Ash getting flung backwards from the cabin and hitting the tree and turning undead.
They recapped the first film at the start of the second because the first film had been a limited release cult indie movie and so they felt audiences needed to be familiarized with the story.
So, in other words, Ash DOESN'T go back to the cabin, he NEVER left. It picks up right where Evil Dead 1 left off.
Army of Darkness (the third film) does the same thing, recapping movies 1 and 2 (with new footage) and then picking up right at the same spot.