Thread causes python.exe has stopped error

I'm developing Server Monitoring Program. I use thread coding to collect several information like cpu, mem, disk, ping etc. And it causes python.exe has stopped error.

APPCRASH Process finished with exit code -1073741819 (0xC0000005)

And error occurs as faster as I use more threads!

Here's my code

    self.thread = Thread(target=self.clntResourceGetter, args=())
    self.thread.start()
    def clntResourceGetter(self):
    time.sleep(5)

     while self.t_flag:
        for client in self.clientList:
            try:
                stdin1, stdout1, stderr1 = self.sshListForResMon[client[0]].exec_command('''free |grep Mem |awk '{print $2" "$3" "$3}' ''')
                stdin2, stdout2, stderr2 = self.sshListForResMon[client[0]].exec_command('''vmstat |tail -1 |awk '{print $15}' ''')

                [...]

                resourceInfoDAO = ResourceInfoDAO()
                resourceInfoDAO.insertResourceInfo(tmpClient)

                except Exception as e:
                    print(e)

        time.sleep(5)

Code is simple. As shown, thread execuetes clntResourceGetter function and it runs forever. Why do thread cause python.exe stop error?