Hi Sujay, As per my understanding there is public transport available to reach Thachi Valley. You first need to take a bus from Delhi to Kullu, Mandi or Manali and get down at Aut. From Aut you will need to take a local bus to Thachi Valley. If not from Aut you can hire a cab or a shared cab to Thachi Valley which wont cost you much. Hope this helps!