The king soon came to consider that the real threat to Siam came from the French, not the British. The British were interested in commercial advantage, the French in building a colonial empire. They occupied Saigon in 1859, and 1867 established a protectorate over southern Vietnam and eastern Cambodia.
Mongkut came to the throne as Rama IV in 1851, determined to save Siam from colonial domination by forcing modernisation on his reluctant subjects. But although he was in theory an absolute monarch, his power was limited. Having been a monk for 27 years, he lacked a base among the powerful royal princes, and did not have a modern state apparatus to carry out his wishes.
When Pridi and the other democratic ministers were forced out of the government and the National Assembly suspended, Seni denounced the regime as illegal and formed a Free Thai Movement in Washington. Pridi led the resistance movement inside Thailand.
The new regime carried out some important reforms. The currency went off the gold standard, allowing trade to recover. Serious efforts were made to expand primary and secondary education. Elected local and provincial governments were introduced, and in 1937 democratic development was brought foward when direct elections were held for the National Assembly, although political parties were still not allowed.
The history of Thailand from 1932 to 1973 was dominated by the military dictatorship which was in power for much of the period. The main personalities of the period were the dictator Phibun, who allied the country with Japan during the Second World War, and the civilian politician Pridi, who founded Thammasat University and was briefly prime minister after the war.
A Lao rebellion led by Anouvong was defeated in 1827, following which Siam destroyed Vientiane, carried out massive forced population transfers from Laos to the more securely held area of Isan, and divided the Lao mueang into smaller units to prevent another uprising. In 1842–1845 Siam waged a successful war with Vietnam, which tightened Siamese rule over Cambodia. Rama III's most visible legacy in Bangkok is the Wat Pho temple complex, which he enlarged and endowed with new temples.
Also in 1939, Phibun changed the country's name from Siam to Prathet Thai, or Thailand, meaning "land of the free." This was a nationalist gesture: it implied the unity of all the Tai-speaking peoples, including the Lao and the Shan, but excluding the Chinese. The regime's slogan became "Thailand for the Thai."
After the Burmese destroyed Ayutthaya, King Taksin was determined not only to drive the Burmese out of Siam or Central Thailand, but also out of Lanna. In the night of February 14, 1775 Chiang Mai fell to the Thai army. Prince Kawila, who helped Taksin in his war in the north, became the first king of Lanna under Siamese rulership.
Ayutthaya was friendly towards foreign traders, including the Chinese, Indians, Japanese and Persians, and later the Portuguese, Spanish, Dutch, British and French, permitting them to set up villages outside the city walls. The court of King Narai (1656-1688) had strong links with that of King Louis XIV of France, whose ambassadors compared the city in size and wealth to Paris.
All that remains of the old city are some impressive ruins of the royal palace. King Taksin established a capital at Thonburi, across the Chao Phraya from the present capital, Bangkok. The ruins of the historic city of Ayutthaya and "associated historic towns" in the Ayutthaya historical park have been listed by the UNESCO as World Heritage Sites. The city of Ayutthaya was refounded near the old city, and is now capital of the Ayutthaya province.
The political environment of Thailand changed little during the middle 60s. Thanom and his chief deputy Praphas maintained a tight grip on power. The alliance between these two was furhter cemented by the marriage of Praphas's daughter to Thanom's son Ranong. By the late 1960s, however, more elements in Thai society had become openly critical of the military government which was seens as being increasingly incapable of dealing with the country's problems. It was not only the student activists, but also the business community that had begun to question the leadership of the government as well as its relationship with the United States. Thanom came under increasing pressure to loosen his grip on power when the King commented that it was time for parliament to be restored and a new constitution put into effect. After Sarit had suspended the constitution in 1958, a committee was established to write a new one, but almost ten years later, it had still not been completed. Finally in 1968 the government issued a new constitution and scheduled elections for the following year. The government party founded by the military junta won the election and Thanom remained prime minister.
The new strain grew easily and abundantly, producing a surplus that could be sold cheaply abroad. Ayutthaya, situated at the southern extremity of the floodplain, thus became the hub of economic activity. Under royal patronage, corvee labor dug canals on which rice was brought from the fields to the king's ships for export to China. In the process, the Chao Phraya Delta--mud flats between the sea and firm land hitherto considered unsuitable for habitation--was reclaimed and placed under cultivation.
The population began to grow explosively as the standard of living rose, and a flood of people began to move from the villages to the cities, and above all to Bangkok. Thailand had 30 million people in 1965, while by the end of the 20th century the population had doubled. Bangkok's population had grown tenfold since 1945 and had trebled since 1970.