RADIUS client-server connection across internet

I'm looking to connect a Point to Site VPN endpoint to a RADIUS server across the internet, and I'm looking for some guidance on whether my understanding is correct. My understanding is having a RADIUS server listening directly on the internet would be bad security-wise, and should not be done, is this correct? Instead, a better architecture would be to connect the RADIUS server and client over a secured channel, like a Site to Site VPN connection. Is my understanding correct here? Would it be fine to connect a client to the server over the internet directly? Is there an alternative simpler solution that I am overlooking? Thank you, -Aaron Peschel