I don't get the meaning of 思うたより


I recently encountered the following sentence

> みんな思うたより緊張しとらんのぉ

I understand it means "everyone is less stressed than I expected." What I
don't understand is why it is 思うたより rather than 思ったより. Is this to represent an
accent/dialect here, like the のぉ instead of なぁ? For the record, this character
uses a bunch of stereotypical western stuff I think.

