Officials went looking for the injured elephant to see if it needed help immediately after the accident at 8:30pm on Sunday.
Khanchit Srinoppawan, chief of the Khao Yai Park, said the spot where the accident occurred has a sign warning motorists to be careful of wild animals crossing.
He said the officials had not yet located the injured elephant by Monday morning.
Police said the front of the truck was damaged but the driver and two passengers were not hurt.