During Ekathotsarot's reign, the English first came to Siam in 1612.
The White Prince was the son of Maha Thammarachathirat of Phitsanulok and Queen Wisutkasat. White Prince had an elder brother who was epitheted The Black Prince and an elder sister the Golden Princess.
In November 1563, Phitsanulok came under attack by King Bayinnaung of Burma. Faced with an overwhelming force, Maha Thammarachathirat surrendered in January 1564, and agreed to join Bayinnaung's assault on Ayutthaya. With Phitsanulok's help, Bayinnaung forced King Maha Chakkraphat of Ayutthaya to surrender in February 1564. Bayinnaung brought back the Black Prince and White Prince, along with Ayutthaya king Maha Chakkraphat. The two princes were educated and overseen by Bayinnaung along with other captive princes.
When Ayutthaya revolted in May 1568, Maha Thammarachathirat remained loyal to Bayinnaung, and became the vassal king of Siam when Bayinnaung's forces retook Ayutthaya in August 1569. The Black and White Prince then returned to Ayutthaya in 1571.
Prince Ekatotsarot joined his brother Naresuan in various wars with the Burmese. Naresuan declared independence in May 1584, and fought off a series of Burmese invasions from 1584 to 1593. In 1590, Maha Thammarachathirat died. Naresuan was crowned as the King of Ayutthaya while Ekatotsarot was made Uparaja but with equal honor to Naresuan (As in the case of Mongkut and Pinklao).
The end of this series of Burmese invasions came in January 1593. Crown Prince of Burma, Mingyi Swa invaded Siam once more, culminating an elephant duel between Naresuan and Mingyi Swa in which Mingyi Swa was slain.
In 1595, Pegu faced rebellions by various tributaries and royal princes. Naresuan planned a massive invasion of Pegu but the city was taken beforehand by the Lord of Toungoo with the support of Arakan. The efforts to capture Toungoo failed in May 1600 and Naresuan decided to retreat. In Lanna, however, a conflict arose between Nawrahta Minsaw the Burmese king of Lanna and Phraya Ram a Siamese-installed Lanna noble. Naresuan sent Ekatotsarot to claim the conflicts by dividing Lanna into two parts.
Naresuan died in 1605 while planning to invade the Burmese Shan states. Ekatotsarot was crowned as his successor.
Upon his coronation, the Ayutthaya kingdom had reached the maximum extent. However, immediately after the coronation, the Lanna kingdom broke away.
In 1612, an English expedition arrived in Siam carrying a letter from King James I of England requesting permission for English merchants to trade in Siam. The King warmly welcomed the party and granted them a station for trading as well as presenting them with lavish gifts. In 1613–1614, Burmese king Anaukpetlun invaded the Tenasserim coast. He gained Tavoy but was driven back with heavy losses at Mergui. (The Burmese then invaded Lan Na in April 1614. Lan Na sought help from Lan Xang but no help ever came, and Chiang Mai fell to the Burmese in December 1614. Note that according to Damrong, in 1618 Siam and Burma reached an agreement in which Burma would control Martaban and Siam would control Chiang Mai. But international scholarship accepts that Lan Na again became a Burmese vassal.
During the reign of Ekathotsarot, a Siamese embassy reached the Dutch city of The Hague, in 1608. The embassy of 16 was brought to Holland by Admiral Matelief on board the Oranje, leaving Bantam on January 28, 1608. The embassy arrived in The Hague on September 10, 1608, and met with Maurice of Nassau, Prince of Orange. This visit coincided with the first recorded mention of the observation of the heavens with a spyglass: the application of a patent by the inventor of the telescope, the Dutch Hans Lippershey, was mentioned at the end of a diplomatic report on the Siamese Embassy, Ambassades du Roy de Siam envoyé à l'Excellence du Prince Maurice, arrive a La Haye, le 10. September, 1608 ("Embassy of the King of Siam sent to his Excellence Prince Maurice, September 10, 1608"), which soon diffused across Europe.
Following the embassy, a treaty was concluded between Holland and Siam in 1617.
Ekatotsarot's reign saw the influx of foreigners into Siam as traders and mercenaries. Ekatotsarot established Krom Asas (i.e. volunteered regiments) of foreign soldiers, for example; Krom Asa Mon, Krom Asa Cham, Krom Asa Yipun (Japanese mercenaries), and Krom Asa Maen Puen (Arquebusiers - the Portuguese and Dutch). Ekatotsarot had a close relations with the Tokugawa shogunate under Tokugawa Ieyasu who commissioned Red Seal Ships to Siam. Around this time the Siamese metallurgists learned the arts of forging mortars from the Westerners and combined with traditional methods giving rise to the praised Siamese mortars known for their qualities.
Ekatotsarot had two legitimate sons: Prince Suthat and Prince Sri Saowabhak. Prince Suthat was invested with the title of Uparaja in 1607. However, only four months later, Prince Suthat asked his father to release a prisoner; but instead angered his father, who accused Prince Suthat of a rebellion. Prince Suthat committed suicide by poison the same night - much to the grief of Ekatotsarot. This is one of the most mysterious historical scenes of Siamese history, as no one knows who was the prisoner Prince Suthat tried to free, nor why Ekatotsarot was so angry. Some historians hypothesized that the prisoner was one of the powerful nobles whose power was a challenge to the monarchy. The nature of Prince Suthat's death was also disputed, as he may have been poisoned by someone else.
Whatever the fact may be, the Prince Suthat incident laid the grounds for future princely struggles that would plague Ayutthaya for about another century. As his son was dead, Ekatotsarot did not appoint his second son, Prince Sri Saowabhak, Uparaja, as expected. It was said that Ekatotsarot died of depression following the Prince Suthat incident, in 1620. Prince Sri Saowabhak succeeded to the throne anyway.
Prince Chula Chakrabongse states, "the king went insane before he died in 1620. His younger son, who had killed the elder brother when their father was alive but helpless, now seized the throne." He became King Songtam, "The Pious" or "The Just", after he repented his act.