In 1601, a group of Dutch traders approached Pattani, a small Thai Vassal state in the south, and sucessfully obtained the permission for building a trading station. One year later, the Dutch East India Company (V.O.C.) was founded and establish their head quarters at Batavia in Java. Backed by this Dutch East India company, the Dutch trading station could be opened in Ayutthaya in 1608, which was the King Ekatosarofs ages. Ayutthaya was the center of international trade which played an important role both as a mainland monarchy and as a maritime power. The Thais were eager to transact with Dutch traders, who exchange their cotton goods with hides and pepper. In order to promote the friendship with the Netherlands, King Ekatosraot sent special envoys to the Netherlands. On June 12，1617，Finally King Songtam signed on a treaty of commerce with Dutch traders. Dutch traders were given the privilege that enabled them to monopolize the trade of deerskin through this treaty. Since it was the time that Portugal’s power was already being weeakened in Southeast Asia, Dutch traders and Btitish traders immediately participated in this competitive market. Because King Narai, the Great of Siam, was afraid of the excessive control of Portugal over Siam, he tried to build a friendship with Dutch and British traders, but his peaceful policy did not succeed. The conflict between the Thais and Dutches started in 1661 when Dutch traders captured a Portuguese ship and took all the goods on the board, which were going to be sent to the Thai King. On the other hand, the Dutch accused Siam of failing to observe the treaty of 1617. In order to secure their interests in trading, they demanded various commercial privileges to Siam, The King of Siam was forced to agree on a treaty of peace on August 11, 1664. The treaty was including many disadvantageous articles to Siam, such as applcation of extraterritoriality to Dutch people, although it was applied only when they are within their trading station. Through this unfortunate event， Thai King realized the substantial threats of the Western worlds. To escape from this difficult situation, Siam attempt to trade with the English for the sake of the blance of power, that is, suppres the power of the Netherlands by giving equivalent power to other European countries that have political interest in Ayutthaya. Fortunate to Siam, the thread from the Netherlands started decreasing as the British traders were successful in building colonies and expanding their market in Southeast Asia. Despite all the conflicts between Dutch traders and Siam, trading was continuted until at Auatthaya was destroyed by the Burmese in 1767.