As mentioned before, two of the discernable categories of Japanese who inhabited Ayutthaya’s Nihonmachi were merchants and warriors.
Japanese novelists and historians seem to agree that most of their countrymen warriors in Ayutthaya were individuals who had to leave Japan under dramatic circumstances, typically after being on the loosing side in one of the last great battles of the sengoku period. Many ronin (wandering and masterless samurai) had to emigrate in order to find elsewhere their lost honour but also to make a living. According to most Japanese writers, it was these men who, thanks to their superior martial skills, were promptly enrolled in the Siamese army and helped Ayutthaya triumph in the never-ending battles against its regional enemies.
While quite a few ronin found their way to Siam, there were others, prior to 1600, who had been fighting alongside the Siamese. A squadron of Japanese asa joined the Siamese army and fought alongside King Naresuan and his brother Ekathtsarot in the crucial battle of Nong Sarai in 1593. The Royal Chronicles of Ayutthaya describe in detail how an army of 100.000 ready to take the Burmese included Phra Sena Phimuk, the Siamese title given to the Japanese military leader in Siam.
However, this report and a couple of minor exploits by Yamada Nagamasa are the only instances when the participation of the Japanese in a Siamese army in the 16th and 17th centuries is confirmed by historical documents. Yet, it cannot be doubted that groups of Japanese warriors were active in the region as, from the late 16th century on, it was common for Japanese to find employment in foreign Asian lands.
The Ming Shi-lu, the Official History of Ming Dynasty, reports that, in 1611, a ship carrying Japanese bound to Ayutthaya capsized when hit by a typhoon. Three men drifted ashore on the coast of China. They were soldiers of fortune, probably going south hoping to get a post in Siam, but they ended up finding employment as Ming border guards.
It seems clear that the Japanese warriors were the most resolute fighters in the region. Besides their skills, the fact that they were immigrant-adventurers without a motherland to return to probably added determination and unpredictability to their character. But, it is improbable that the Japanese played key roles in the battles of the Siamese army. It is however clear that a group of Japanese warriors, numbering around 500-600, formed the royal bodyguard, as we know that they were used in the case of emergency, for example in 1624. They also played a pivotal role in the events that followed the death of King Song Tham in 1628.
Facts prove that, in the 17th century Ayutthaya, the Japanese more than any other foreign group were involved not only as trade partners, but also politically and military. The ultimate evidence comes from the fact that the Japanese, over a span of a little more than fifty years, were involved to some extent in three thorny royal successions that were characterized by coups and violence in 1612, 1628-30 and 1656.
Resources: “Samurai of Ayutthaya – The Historical Landscape of
Early 17th Century Japan and Siam: Yamada Nagamasa
and the Way to Ayutthaya” by Cesare Polenghi (p. 26-35)
