Hi Friend,
There are two solutions for your requirement,
1. Create a VPN from the remote location ( where AP is connected) to the location where the Controller is deployed and provide the Master IP to the AP ( Static, DHCP option 43/60 or through DNS)
Bottom line, AP should be able to discover the Master and should be able to exchange the PAPI traffic with controller.
2. Connect the AP directly to the controller and provision the AP as a RAP and take it to the remote location and uplink it .
Ensure that all the required VPN related config is taken care and the required traffic is allowed in the firewall either side.
Hope got some clarity on this,
Please feel free for any further help on this.