Prince Damrong believed that the "Khun Chang Khun Phaen" story was based on true events which took place around 1500 in the reign of King Ramathibodi II. His evidence was a memoir believed to have been taken down from Thai prisoners in Burma after the fall of Ayutthaya in 1767 ("Khamhaikan chao krung kao", The testimony of the inhabitants of the old capital). The memoir mentions the name of Khun Phaen in an account of a military campaign against Chiang Mai. However, this memoir is just as much a text of oral history as "Khun Chang Khun Phaen" itself, and could well have developed from the folktale, rather than vice versa. The campaign against Chiang Mai in the latter part of "Khun Chang Khun Phaen" seems to be modeled on events which appear in the Ayutthaya and Lan Xang chronicles for the 1560s.