How to identify a Windows Remote Desktop user by SQL Server session id?
One way to accomplish this would be to use the host_process_id column from sys.dm_exec_sessions

This host_process_id in this table maps to the PID in task manager.

In this case we could run the following query to get our host_process_id, and then take the result and check in task manager which application currently has a PID matching the result.

SELECT session_id, host_process_id FROM sys.dm_exec_sessions WHERE session_id = XXX


You can then check which account is running that process.