Yes, it is possible, but depending on where some of these locations are, I would strictly reject to mange them remote .
yes it's possible to manage all those hosts with one vCenter server. Best practice would be if all locations were connected through a VPN network to secure the traffic.
A requirement would be to open some ports so vCenter can talk to the ESXi servers.
A full list of ports can be found here:
Can we use MPLS as it will allow the ESXi hosts to be added to domain, use domain authentication?
if MPLS is there, then it is cool no need to do any extra things, you can add to domain also.