meaning - Why is ば in this sentence?

そんなトコで何ばしよる。

I'm reading a manga and from the context of the pictures I think this sentence reads, "What are you doing up there," but I have no idea what part ば plays. The character speaks in a dialect so my confusion could be a result of that, but any help would be much appreciated.

Answer

ば is the accusative particle used in wide area of (northern, as I remember) Kyushu as much as を in Standard Japanese. Etymologically it's from を + は contracted but no longer has share the は sense in Standard Japanese, as we can see that it's able to mark the question word (thanks to @user4092).

そんなトコで何ばしよる。

means

そんなとこで何をしてる（んだ）。

or a bit more textbook-friendly,

そんなところで何をしている（のだ）。