Rattanakosin Kingdom or the Kingdom of Siam (Thai: อาณาจักรรัตนโกสินทร์, IPA: [āːnāːt͡ɕàk ráʔtànákōːsǐn]; 1782 – 1932) was the fourth Thai Kingdom, and was centered at the city of Bangkok. It included vassal states of Cambodia, Laos, and some Malay kingdoms. The kingdom was founded by King Buddha Yodfa Chulaloke of the Chakri Dynasty. The first half of this period was a time of consolidation of the kingdom's power, and was punctuated by periodic conflicts with Burma, Vietnam and Laos. The later period was one of engagement with colonial powers of Britain and France, in which Siam managed to be the only southeast Asian nation to escape European colonialism. Internally the kingdom developed into a modern centralised nation state with borders defined by its interaction with the Western powers. Significant economic and social progress was made, with an increase in foreign trade, the abolition of slavery and the expansion of education to the emerging middle class. However, there was no substantial political reform until the absolute monarchy was replaced in a revolution in 1932 by the constitutional monarchy.