At the end of the 18th century the provinces of Battambang and Siem-reap were annexed by Siam.
In 1867 a treaty between France and Siam was signed, whereby Siam renounced its right to tribute and recognized the French protectorate over Cambodia in return for the provinces of Battambang and Angkor, and the Laos territory as far as the Mekong.
In 1904 the territory of Cambodia was increased by the addition to it of the Siamese provinces of Melupre and Bassac, and the maritime district of Krat, the latter of which, together with the province of Dansai, was in 1907 exchanged for the provinces of Battambang, Siem-reap and Sisophon.
In 1907 a further convention was made with France, Siam returning to the French protectorate of Cambodia the province of Battambang conquered in 181r, and in compensation receiving hack from France the maritime province of Krat and the district of Dansai, which had been ceded in 1904.
In 1875 sapphires were discovered in deposits of clay and sand in Battambang (Siam), where they have been worked on a considerable scale.