Thaification is the process by which people of different cultural and ethnic origins living in Thailand become assimilated to the dominant Thai culture, or more precisely, to the culture of the Central Thais. Thaification is a step in the creation in the 20th century of the Thai nation state where Thai people occupy a dominant position, away from the historically multicultural kingdom of Siam.

Thaification is a byproduct of the nationalist policies consistently followed by the Thai state after the Siamese coup d'état of 1933. The coup leaders, inspired by Western ideas of an exclusive nation state, sought to increase the power of the Central Thais. The businesses of interspersed minorities, like the traditionally merchant Thai Chinese, were aggressively bought out by the state, which gave preferential contracts to ethnic Thais. Thai identity was reinforced both in the heartlands and on the fringes. Central Thailand became economically and politically dominant, and its language became the language of the media, business, and education. Equally, its values became the national values. Central Thai culture’s being the culture of wealth and status made it hugely attractive to those on the edge economically and socially.