If you are traveling through Fukche-Koyul-Demchok-Umling La, then you will need special permits signed by the District Magistrate of Leh. If you are traveling through Hanle-Photi La-Umling La route, then the regular permit obtained from Leh is sufficient.
For NRI PAP needs to be applied. You need to apply online. There is a fee to be paid. Once your permit is through, make enough copies to submit at check post. This permit is valid for a week. If you are extending stay then re apply for extension.