Meaning: 何を考えてるの？（少し冗談っぽく言う表現）
For Example:
‣ You've been keeping silence for a long time, a penny for your thoughts!
長い間黙りこくっとるね。何考えとんか教えていた！
‣ What's with the pensive look? A penny for your thoughts.
物思いにふけってどしたん？何考えとん？
Synonym:
What's in your mind?
What are you thinking about?