After the 1688 Siamese Revolution, most foreigners were expelled from the kingdom; foreign influence dropped to minimal levels. That situation remained for almost 140 years. However, Western nations, especially the U.K. and the U.S., started looking for new markets for their exports. These countries showed in Bangkok in the late 1810s and early 1820s eager to resume trade and diplomatic relations. However, the Thais were wary since they saw the surrounding nations were being absorbed into European colonial empires: India, Burma, Vietnam, Malaysia, Indonesia, China seaports, the Philippines and Singapore. They did not wish to meet the same fate, so they initially resisted these commercial and diplomatic overtures and planned to move slowly. But foreign nations were determined to establish relations so the Thais knew it would only be a matter of time before they had to work out some agreements.
The Portuguese were the first to set up an embassy in 1820. The first agreement between the U.K and Thailand called Burney Treaty signed in 1826, but this was not about commerce. Thailand and the U.S. signed a treaty in 1833. It was the first treaty the U.S. signed with an Asian nation. but nothing much came out of it. Only a few European and other foreign traders appeared, but most of the Westerners who arrived during this time were Christian missionaries who doubled as teachers and doctors, both very prestigious professions in the eyes of the Thais. However, trade had always continued with China. Chinese junks of all sizes plied the waters carrying mainly rice and other local commodities to home and all manner of goods to Thailand including porcelain wares, teas, cutlery, silks and thousands of other little trinkets and useful objects. Trade between Thailand and the Dutch East Indies plus Singapore consisted of mainly European goods and textiles.
However, everything dramatically changed overnight when Sir John Bowring, the British Governor of Hong Kong, arrived in Bangkok. He negotiated a trade agreement with King Mongkut (King Rama IV) that was signed in April 1855. In short, the treaty was similar to the forced treaty signed between the U.K. and China, namely one that was unequal or heavily skewered toward the British. Although the agreement liberalised foreign trade between the two nations, the Thais were pressured to accept and not allowed to negotiate under the veiled threat of armed force.
In the eyes of the Thais the treaty provisions included sweeping changes. It created a new system of imports and exports with fixed low customs duties. There would be one tax only, all other different taxes on the same goods would be abolished. All royal monopolies were terminated, heavy royal taxation on imports was ended and tree trade guaranteed for all foreigners in Bangkok. Thailand reserved the right to prohibit the export of rice, fish and salt if these commodities proved to be scarce. A British consulate was authorised, and British subjects could own land, subject to some restrictions. As with all such treaties at the time, British subjects were given the right of extraterritoriality in that local authorities could not prosecute British subjects without consular approval. British subjects could travel inside the country and trade freely with locals without interference. But the treaty also allowed British ships to import opium. The treaty was very important in one aspect. It prohibited all other nations from interfering in Thailand’s internal affairs thus guaranteeing the country’s independence.
The effect of the treaty was dramatic. It created a framework for trade between Thailand and China and Singapore. Trade started to increase exponentially. Within two years there were 200 Western ships that called on Bangkok. Rice became a major export commodity to British India with sugar cane and teak becoming import exports. Quickly other nations signed bilateral treaties with Thailand, including the U.S. in 1856, all based on the Bowring Treaty. Foreign embassies started to be quickly set up and foreigners started pouring into Bangkok, although they had to live on boats along the river. Trade and commerce started to greatly accelerate. The Thai government eventually shifted to a tax farming scheme by granting concessionary licenses to make up for the loss of royal monopolies on such activities that included teak, gambling and opium. In the end of the Thai government gained in the bargain with much higher revenues.
The Bowring Treaty proved to be a great boon to the country as trade was greatly expanded.