hi, can I install an additional basebord heater in my basement, and wire it directly to my wall mounted thermostat, instead of wiring it directly to the existing baseboard heater. Because it is easier for me to fish from the thermostat to th new heater, than to the existing heater, that is on the other end of the room (16 x 20 room)

Are you attempting to control one system with 2 separate stats? If so then the answer is no.

No I want to control 2 heaters with 1 t-stat, but fishing the wire from existing heater to the new one will pose more of a task, that fishing the wire from the t-stat to the new heater

Electric baseboard heat I assume? What is the voltage rating? What is the rating on the stat?

Your best bet is to run a separate electrical circuit and separate thermostat to the new heater you want to install. This way you will know the wiring and control for the heater will meet the code requirements for the install and it will be safe. The wall mounted thermostat will have to be designed to control the voltage for the new heater. Most heaters are 240 volt but some can be had that operate off 120 volts.