play for a fool

play (one) for a fool

To presume or believe that one is very stupid or foolish, or to treat one as such. I'd advise you not to play her for a fool. She may play dumb, but she's very crafty.
See also: fool, play

play someone for a fool

Fig. to treat someone like a fool; to assume someone is naive or stupid. Don't play me for a fool. I won't have it. You are playing me for a fool! Stop it!
See also: fool, play