This unused card has no caption and no attribution apart from its own index number of 500 1522.  But if you were in Thailand, you would be expected to know exactly who everyone was.  We are not experts, but judging from the ages of the individuals, we might guess the photo to have been taken in the 1970s.  And if by chance you don’t know, the (new) King is the man standing in the back row along with his sister.  Grade: 1