Thanos replaces Thor....meaning Thanos is amped by Norn Stones at a stage in this fight.
Thor was about to be destroyed by the Void until Void was distracted and sought better prey.
In the end Stark crashed a Helicarrier into Void resulting in the Sentry persona emerging, who wished death.
And who better than Thanos to give it? If he still retains Death Avatar status it's too easy.
The only advantage Thor has over Thanos in this particular fight is Thor's maneuverability.
The Void killed Loki and Ares who were grounded fighters quickly. And both were Gods. Though I don't see Thanos taking on the Void as sacrificially as Thor did during the event.
But once those Norn Stones take effect...game on! Petty superhero powers took painful damage to the Void.
Add that to Thanos and it's party time.
Sorry but Thanos wins. And this isn't a real forum fight, it's a reamginaning of a past battle. Even if the Void destroyed Thanos he would simply return within a 5 seconds and finish him later.