Resumption of Power After the Burmese retreat, the two kings Ekkathat and his younger brother
Uthumphon seemed to peacefully coexist for a while in the royal court. In order to reduce the influence of Ekkathat's two consorts, Uthumphon ordered Princess Maengmao, a daughter of King Borommakot born to a secondary consort, who had been a Buddhist nun, to leave her nunnery to become a consort of King Ekkathat in 1760. Ekkathat made his half-sister Princess Maengmao his chief queen with title Kromma Khun Wimonphat (), given her high birth status as a royal princess. Queen Wimonphat bore a princess, Princess Si Chanthathewi. Things took a negative turn when, on one day in the waxing of the eighth month this group of Mon refugee men at Nakhon Nayok, called
Mon Mai or the "New Mons", arose in rebellion due to oppression by local Siamese officials. The Mon rebels took position of Khao Nangbuat Mountain in modern Sarika,
Mueang Nakhon Nayok district to the northeast of Nakhon Nayok town. Lacking modern firearms, the Mon rebels armed themselves only with melee wooden sticks. King Ekkathat and Ayutthayan royal court responded by sending the royal forces of 2,000 men In 1718, James Collison, a representative of
Joseph Colett the
British governor of Madras, arrived in Ayutthaya in the reign of King
Thaisa to settle some trade disputes. After the death of Alaungpaya in 1760, his son and successor the new Burmese king
Naungdawgyi sent Burmese forces of 7,500 men under Abaya Kamani and Minhla Thiri (who later became
Maha Nawrahta) in October 1762 to attack and conquer Chiang Mai and
Lamphun. Facing an overwhelming Burmese invasion, in December 1762, the ruler of Lamphun and his
Northern Thai subjects fled their town to take refuge at
Phichai, a Siamese frontier town to the southeast of Lamphun. King Ekkathat then ordered the ruler of Lamphun and other Northern Thai refugees to move down south to take shelter at Banglang the northern
Khanon or riverine duty checkpoint on the
Lopburi River in the Phosamton neighborhood about five kilometers to the north of Ayutthaya in modern
Bang Pahan district. King Ong Chan of Chiang Mai sent a request to Ayutthaya for military aid against the Burmese invaders. King Ekkathat of Ayutthaya responded by sending Northern Siamese forces of 5,000 men under
Chaophraya Phitsanulok Rueang the governor of
Phitsanulok to aid Chiang Mai. However, Chaing Mai fell to the Burmese in August 1763 before the Siamese relief forces could reach Chiang Mai. King Ong Chan of Chiang Mai, along with his Northern Thai subjects, were deported wholesale to Burma. The Siamese, who had already reached
Tak, did not engage with the Burmese and simply returned. Burmese conquest of Lanna was detrimental to Siam's geopolitical situation as Lanna would become the base for Burmese military operations in the region, providing the Burmese with vast manpower, supplies and other resources.
Submission of Tavoy Burmese king Naungdawgyi died in December 1763, succeeded by his younger brother Prince Myedu, who ascended the throne as the new Burmese king
Hsinbyushin. Hsinbyushin, formerly Prince Myedu, led the vanguard force of his father Alaungpaya during the
Burmese invasion of Siam in 1760 and had an opportunity to learn about Siamese geography and military tactics. His experience in Siam would affect and influence the Burmese strategy on the upcoming Burmese invasion of Siam in 1765 that would eventually led to the fall of Ayutthaya in 1767. The Burmese gained control of
Tavoy in December 1759 or January 1760 during Alaungpaya's campaign. Tavoy had been under attack by rebels since 1761, according to the writings of
Pierre Brigot the
vicar apostolic of Siam. Udaungza, a Burmese official, seized control of Tavoy some time after and killed the Konbaung-appointed governor there. After the demise of the Burmese king Naungdawgyi, in December 1763 or early 1764, Udaungza the self-proclaimed ruler of Tavoy sent tributes to submit to Ayutthaya. Siam then assumed control over the whole
Tenasserim Coast from Tavoy to Mergui, though this control would be short-lived. == Burmese Invasion of 1765 ==