Depends on several things such as make of tyres, whether or not you have rim locks fitted, and the type of terrain you are going to go over. But for your KTM, 14 or 15 p.s.i. should be about right. For pure road use the pressures should be higher.
I have used much lower pressures before if it's really soft, even ran the rear flat one day after a puncture.
Roy.