Python TypeError: start_new_thread expected at least 2 arguments, got 1

>>>
>>> import thread
>>>
>>>
>>>
>>> def fun1():
...     print "hi"
...
>>>
>>>
>>>
>>> thread.start_new_thread(fun1)
Traceback (most recent call last):
  File "", line 1, in
TypeError: start_new_thread expected at least 2 arguments, got 1
>>>
>>>
>>>