I have a Vmware guest with two network adapters. Both adapters are on a different subnet.
Can we connect using RDP to the second network adapter?
As long as the 2nd NIC is routable from where you are RDP'ing from (eg vLan / Subnet / network / switch / firewall / etc), then yes, you should be able to RDP to the 2nd NIC
You may just want to be aware though that you will either need a separate DNS entry or use the IP address for the 2nd NIC, if you only have one dns entry for the server (pointing to the 1st NIC)