I don't think there is direct evidence, but you can certainly interpret it as either suspicion or just plain old curiosity. At the beginning of the scene, Banquo notes to Macbeth that part of the witches' prophecy has come true for him (Macbeth - already with the title of Glamis and now with Cawdor's title). Banqo says "To you they have show'd some truth.' Banquo says he's had a dream about the sisters (witches). First Macbeth says he hasn't thought of them, which is curious or suspicious in itself. How could he not have contemplated the recent and strange event of 3 witches predicting his immediate future? What should arouse more suspicion/curiosity on Banquo's part is when Macbeth follows, saying that they will "have some words upon that business." First he says, 'haven't even thought of it.' Then he says, 'we'll talk about it later.' Certainly suspicious.