GRAND PALACE
1351 - The first Grand Palace of Ayutthaya.

The first palace built at the establishment of the City of Ayutthaya in 1350 stood, where
is today the ruin of Wat Sri Sanphet. The original buildings were likely constructed in
wood. [1]

"The Brahmans, having selected an auspicious moment, held the Rite of
Atonement and obtained a conch shell, which turned to the right, beneath a
sebesten bush. Then
the Phaithun Palace, the Phaichayon Palace and the
Aisawan Palace
were built. [B: And the King] [CDEF: Then King U Thòng]
entered the city and ascended the royal throne. [F: The age of the King at that
time was thirty-seven.] The Brahmans bestowed upon him the royal title of King
Ramathibòdi I of the Capital City of Ayutthaya."
 [2]

In the second reign of King Ramesuan (r. 1388-1395) we find in the Royal Chronicles
of Ayutthaya an indication of the existence of a
Mangkhalaphisek Hall. This hall
could have been an element of one of the above mentioned wooden palaces and used
for the king's devotional Buddhist practice which included daily rituals taking refuge in
the Triple Gem and undertaking to observe the five precepts, but it could also have
been part of another structure in the palace such as the three-porticoed hall (Trimuk
Hall), mentioned later in the texts. The entry of the hall was likely directed to the east
and probably sheltered a large Buddha image.

"Then the King went out to observe the precepts at Mangkhalaphisek Hall. At
ten thum he looked toward the east and saw a Great Holy Relic of the Lord
Buddha performing a miracle."
 [3]

"In 749, a year of the hare, ninth of the decade, the Phukhao Thòng Monastery
was founded. One evening the King walked to
Mangkhalaphisek Hall; and Thao
Mon, who had died earlier, came and sat blocking the path where the King was
walking and then vanished."
 [4]

In the Royal Chronicles of Ayutthaya, we read that in the reign of King Borommaracha
II (r. 1424-1448)  in two succeeding years 1440 and 1441 a fire broke out the royal
palace and reference is made of the Trimuk Hall (three-porticoed hall).

"In 802, a year of the monkey, a fire broke out and burned down the royal
palace."
 [5]

"In 803, a year of the cock, a fire broke out and burned down the Trimuk Hall."  
[6]

When King Borommatrailokanat (r. 1448-1463) came on the throne in 1448, he
converted the palace site into a royal monastery and built a new palace to the north of
the old one, closer to the
Lopburi River.

References:

[1] Guide to Ayudhya and Bang-Pa-In - Tri Amatyakul (1957) - Prachandra Press,
Bangkok / Phraya Boran Rachathanin in Tamnan Krung Kao.
[2] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 10 /
Source: Phan Canthanumat, British Museum, Reverend Phonnarat, Phra
Cakkraphatdiphong & Royal Autograph - King Ramathibodi I, 1351–1369.
[3] Ibid. - King Ramesuan [Second Reign], 1388-1395- page 13.
[4] Ibid. - page 14.
[5] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 15 /
Source: Luang Prasoet - King Boromracha II, 1424-1448.
[6] Ibid. - page 15
1448 - The new Grand Palace

(In construction)
Sketch of the Grand Palace
Excavation plan of the Grand Palace
(Sketch of the Grand Palace)
(Excavation plan of the Grand Palace)