A peak-human vs the Norse god of thunder — not even Batman's prep can bridge this gap easily.
Batman vs. gods is always interesting because Bruce has actually beaten gods before — but always with specific preparation targeting specific weaknesses. Thor doesn't have a convenient weakness like kryptonite.
Thor's power comes from divine enchantment, not technology that can be hacked or a biological vulnerability that can be exploited. Mjolnir's worthiness enchantment means Batman can't even pick it up. Thor's lightning is magical, not electrical, so standard insulation doesn't help.
Without prep, this is a non-contest. With prep, Batman would need to find a way to neutralize divine magic — which is theoretically possible given DC's magical resources, but far more difficult than his usual contingency plans.
Batman has defeated divine-level opponents with preparation. He has access to DC's magical resources through Justice League connections. His tactical mind could find unexpected approaches to counter divine power.
Thor has no convenient weakness to exploit. Mjolnir's power is magical and divine, not technological. Thor's physical stats exceed Batman's by orders of magnitude. Even with prep, Batman's options against a Norse god are extremely limited.
Thor wins in the vast majority of scenarios. Batman's prep-time superpower hits its limits against divine beings with no exploitable weakness. This is one of the few matchups where even 'Batman with prep' isn't a convincing argument.
Batman also fights
Thor (Norse) also fights