Unidentified photographer
1868 (or earlier)
King Mongkut or Rama IV with his son the future King Chulalongkorn

Photograph
Creative Commons - Wikipedia
Source requested.
 
Circa 1866 , as the teenage boy shown, Chulalongkorn, was born in 1853 and appears to be about 13 here. The older man in the photo, Mongkut, died in 1868, so the photo must have been taken by 1868.
 
LL/116950