GST/ ISD REGISTRATION for Rent paying to individual

we are pvt ltd company registered at Delhi.

we have a display center at Himachal pradesh and paying rent Rs 3Lac per month.

1) we are not register at HP.
2) paying rent to 3 persons Rs 1 Lac each. All three are unregistered.

my question is
a) we need to be register? as we both are unregistered at HP.
if yes, then which registration i required GST/ISD or both?

(for RCM i should be registratered as GST. in this Case how i can take input?)

Need expert opinion......