What happened to this airplane at Lombok Airport?
(Source)

The aircraft's registration is PK-YVL. It's a Boeing 737-300 that was operated by Batavia Air before the airline ceased operations.

This plane is/was leased from Pacific AirFinance. It has been withdrawn from use and stored at LOP since 31 Jan 2013. After ceasing operation, some of the other 737-300's the airline had were delivered to Peruvian Airlines.

Due to its proximity to parked aircraft, it's not likely the plane has been converted to train firefighters. The darkened area could just be storm blown mud.

(Source) Same plane, previous operator.