Judging on their past fights, I say Thor wins this.
I don't see how SS can continue to stop that hammer from hitting him throughout the entire fight. I mean SS can maybe dodge some but not all. I'm also beginning to think that Thor's hammer is SS's krytonite. For one good hit to the face seems to take SS pretty much out of it. Once dazed by the first good hit , Thor can maybe pile on more for the instant ko.
Now Thor is hella resistant against energy based attacks. So I don't think SS can hurt Thor too much until Thor hits him with the hammer. Plus Thor can be flying around in evasive mode too. Thor might even absorb some of that energy with the hammer.
And I've have yet to see SS attack while phased. So most likely attacking while phased is not an option for SS. Now SS can decide to stay phased the entire fight for the stalemate though.