The most ancient civilized country in South-East Asia is Khmer, while Siam just created their own nation in 13 century A.D. I don't know why Firaxis decide to choose Siam instead of Khmer, because as I know about the history, most ancient temples in Siam are get from Khmer. It is very a shame that forget this brilliant Civilization as Khmer (Cambodia) and hope Firaxis will choose Khmer in the next pack,