There is a relatively unknown bat cave north of Khao Yai National park where every night several million bats exit to start their night of feeding. Finding out about this cave was pure luck. An acquaintance of ours was a friend of some of the forest rangers of KYNP, and when one of them found out about my wife's love of bats, he went with us on his own time to witness the bats exiting for the night. The cave opening was several hundred feet up and once the exodus began, it was like black smoke pouring out of the cave. The bats rode the air currents and the stream would frequently dip to just above our heads. This was shot facing away from the cave opening.