Complex sentence: The last place where it was hoisted was in the final area held by the FANK forces on the escarpment of the Preah Vihear Temple in the Dângrêk Mountains that fell to the Khmer Rouge on 22 May 1975.
Split into simpler sentences: The last place where it was hoisted was in the final area held by the FANK forces on the escarpment of the Preah Vihear Temple in the Dângrêk Mountains. Finally that outpost fell to the Khmer Rouge on 22 May 1975.