Hello Sean Sok Phay,

In 1904 map was provided by the French to both Cambodia and Thailand, that map in 1904 this year was that the French has given 3 provinces of Cambodia to Thailand, 1) Battambong 2) Seim Reap 3) Preah Vihear. In 1904 Cambodia also has 3 of Siem provinces ( sorry I do not remembered its name but you can check them out at the former King Norodomsihanuk website).

In 1907 the French thought that was a wrong ideas to give Siem our Khmer 3 provines, so then the French decided to swap those 3 provinces back to Cambodia, and that provinces what we have now Siem Reap, Battambang,and Pheah Vihear.

In additional to these matters and map its all recorded and well kept in Paris, France. And that is why in 1962 ICJ decided that the Preah Vihear province is belongs to Cambodia.

Good luck with your study!