By the mid-nineteenth century, Siam changed significantly because the European powers had expanded their political and trading activities into Southeast Asia, including Siam. The commercial treaties of the 1850s started the process of bringing Siam into an orbit of modernity. To fit the new “international standard”, the Siamese government needed to create “Bangkok Modern” following the West. One of the main points this study found is that the modernizing of Bangkok made the landscape of the city change from a moat-fortified city to a modern city with a form of Western modernity. This dissertation also makes the argument that the transformation of Bangkok commenced gradually from the reign of King Mongkut, not, as it is commonly believed, after the First Grand Tour to Europe of King Chulalongkorn in 1897. More importantly, Bangkok under King Mongkut and King Chulalongkorn adopted a form of modernity from “the colonial modernity”, using Singapore and Batavia as models as both King Mongkut and King Chulalongkorn were more familiar with these cities than other colonial cities. As evidence of this, King Chulalongkorn visited Singapore and Batavia 26 years before going to Europe, and it was during this 26-year period that reforms changed the appearance of Bangkok. This can be seen through the construction of roads, shop-houses, and a modern infrastructure that were influenced by Singapore and Batavia.