Complex sentence: Modern map surveying in Thailand began in 1875 during the reign of King Chulalongkorn (Rama V) with the establishment of a Mapping Division to lay out the map for telegraphic activities linking Bangkok to Phra Tabong (Battambang) and also to map around the Thai Gulf.
Split into simpler sentences: Modern map surveying in Thailand began in 1875 during the reign of King Chulalongkorn (Rama V). A Mapping Division was established to lay out the map for the telegraphic activities linking Bangkok to Phra Tabong (Battambang) and also to map around the Thai Gulf.