Yes you can, there is a direct regional train every hour at xx:43 and it does not have reservations.

Edit: oops, I overlooked that it's a one country pass, indeed only valid until Chiasso.

Note that a one-country Italy pass is valid as far as Chiasso. Then you need a regular ticket available on sbb.ch or SBB app. It also includes buses and the little funicular in Lugano.

(Using a pass day might not be worth it.)