This Pole looks like he is wearing a Turban.
Hi mate,
If memory serves, this portrait appears in the Osprey Men-at-Arms series of books, in the Polish military edition. I think the subject was an Oginski, or the leader of a mercenary Polish outfit in Western Europe, painted on his reurn to Poland circa the Swedish Wars in the 1650's, as I recall the commentary to the portrait.
I'd have to say his hat is a kolpak, progenitor of the busby and other fur trimmed cavalry hats. Cheers.