What does this mean?

Siam, the ancient name of China for Thailand, a Southeast Asian country, is Sayam in Thai and Siam in English. The main ethnic group is Thais, and those who believe in Buddhism occupy the first place. Since the establishment of13rd century, it has experienced four times: Sukhothai, Ayutthaya, Wuli and Bangkok. On June 24th, 1939,/kloc-0 changed its name to "Thailand",/kloc-0 changed its name to "Siam" in 1945, and/kloc-0 changed its name to "Thailand" again in 1949, which is still in use today.