I have an android phone that I want to monitor the HTTP/https traffic using tools like CHARLES PROXY but the phone not on the same network as the CHARLES PROXY host. is there a way to do that without using an external server?
There is no need for an external server. You need to route the traffic from your phone to the device where the intercepter is running. You could create a mitm setup with a tool like https://mitmproxy.org/. Btw you will need a routed phone, something like xposed-ProxyOn.. Then you can intercept app specific traffic. But if you try to intercept https traffic from apps they use certificate pinning you wont get a connection to the app server