bearing in mind that my Thor knowledge is limited to Simonson and some Avengers...
Current 616? I think Thor still has the Odinpower (because despite his exile, Thor can still move Asgard while Baldur can't), in which case Diana's boned. (Byrne-era full-blown-goddess Diana might have been a match for him, though; I haven't read enough Thor to really get a sense of what the Odinpower really entails).
Without the Odinpower... more complicated. Rumbles forums tend to put a lot of emphasis on the speed blitz, which is pretty fair - if you can move near the speed of light and your opponent can't, most other considerations become secondary, and while Thor's got above-human speed, you don't see him race Pietro or anything (and even if you did, Marvel fast is not like DC fast). There's also the she's-worthy-of-Mjolnir thing to consider - between the tiara and the lasso she's got significant range on him, which she can use to provoke him into throwing his hammer*, and if he does, she can just catch it and beat his head in. On the other hand, he punches harder than her even before you add in Mjolnir, and can take more damage**, and actually has martial training, so if it gets down to melee and lasts more than a round, he's going to come out on top.
So, assuming they're meeting for the first time on the battlefield, Thor wins - Diana never speed blitzes or attacks from range out-of-the-gate, always defaulting to realtime melee, so the advantage and the fight is Thor's. Assuming they're familiar with each other's powersets, though, Diana can manage a victory by fighting tactically and pulling out all the superspeed stops.
* Or summoning lighting, but the only time I've seen him do that, it appeared to have a casting time, and Diana could take it on the bracer anyway. ** Assuming average power levels. If Thor is Clark or Billy's match, he's stronger than Diana, which isn't consistent with Diana being able to pull a third of the Earth out of orbit (unless Thor's tossed planets around in something I haven't read, I admit my knowledge of him isn't nearly as extensive), but that's an outlier compared to their respective average performance, so I think it's still fair to say he's got her here.