The northern wall of the Grand Palace
The northern wall of the Grand Palace, situated along the main river (2), was part of the city wall of Ayutthaya. The wall was 4 meters high from ground level to the base of the parapet. The breastwork was one meter high, which made the palace wall 5 meters high and 3 meters thick (3), while an allure or Chemin de ronde for the guards ran below the battlements. Between the two corner forts forming the northern wall of the palace, there were six gates. Some sources mention an additional gate called the Pratu Jan Thawan Phirom, being the first gate in the northern wall (thus west of Earth Gate).
East of the Phak Tho Gate stood the Phak Tho Fort, also known as the Thai Sanam Fort, a corner fort. The first gate in the northern palace wall was the Bowon Nari Maha Phop Chon Gate, also called Pratu Din or Earth Gate, given out to Earth Gate Road.
The second gate was Maha Trai Phop Chon Thawara Uthok Gate, or Water Cloister Gate, leading to the Wasukri Landing on the main river.
The third gate was the Sao Thong Chai Gate, or Victory Flagpole Gate, an elephant-ear gate.
The fourth gate was the Jao Prap Landing Gate. (4) This gate was used to go out from the palace in the case of ceremonies.
The fifth gate was the White Elephant Gate, used by white and other royal elephants to bathe in the river.
The sixth and last gate was the Khoi Landing Gate, also known as the Nobles Landing Gate, giving the palace officials access to the Nobles Landing ferry. (5)
Finally, we had the Tha Khan Fort or Boundary Landing Fort, again a corner fort standing at the northeast side of the palace.
In 1759 CE, King Alaungpaya (reign 1752-1760 CE)
, after having taken the cities of Tavoy, Mergui, and Tenasserim, came down to Ayutthaya through the Singkhon outpost. Ex-king Uthumphon (reign 1758 CE), persuaded by nobles and imperial subjects, left the monkhood and undertook the defences of Ayutthaya. The northern palace wall, which was also part of the city wall, was believed to be too close to the palace buildings. Another wall, farther removed from the palace but slightly lower than the old wall, was constructed to enable the guns to be fired from the old wall and new wall. This new wall likely followed the present U-Thong Road from Wat Thammikarat to Khlong Pak Tho, bending around the palace.
"Now the walls of the municipality along the front of the Holy Royal Palace Enclosure on the side toward the edge of the river originally consisted of only a single tier. He had one more tier of walls newly constructed outside and lower than the original walls. And He had teak logs brought up, tied to hang from the boundary stones and pounded into the ground to form barriers to seal off all the water and land gates." [1]