Resongtso Lake is not within the official Park of Yading.
Resongtso is shown on map as Soka Lake. It is a small lake at the southwest of Mt Chenrezig at over the pass of Songduo heading north to Kasi Valley and on the Yading Small Kora Trek. It is at the elevation of 4500 meters above sea level. The usual tourist visit doesn't go this far to this lake.
Route: Chengdu - Siguniang - Tagong - Yading - Xinduqiao
Route: Daocheng - Yading - Daocheng
Route: Daocheng - Yading - Daocheng