Thank you to the globetrotting philatelist, Ronald! This 1998 aerogramme shows a face from Bayon, a temple at Angkor Archaeological Park within Angkor Thom.
Thank you German! This 2011 stamp shows Henri Mouhot, the Explorer-Naturalist who brought world attention to Angkor. A Bayon smiling face is in the background.A photo I took of one of the many hallmark smiling faces at Bayon on a 2016 trip.