The two chedis from the early Ayutthaya period are located in central Ayutthaya on
the crossing of Naresuan Rd (former Pa Than Rd) and the Chikun Rd next to the Pa
Than Bridge, opposite Wat Rachaburana.
In situ are the ruins of two brick chedis dating from 1424, each with an octagonal base.
Chedi Ay Phraya (the smallest ruin) is situated north of Chedi Yi Phraya. Following the
Fine Arts Department the two chedis were surrounded by an outer wall, although no
History relates that King Intharaja I had three sons, named according to the old
numerical system (Ay = first, Yi = second and Sam = third). On the death of their father,
in 1424, the two elder sons, Ay Phraya living in Suphanburi, and Yi Phraya leaving in
Sanburi, fought for the throne here in Ayutthaya. Both princes engaged each other in
personal combat, mounted on elephant; on or near the "charcoal forest" bridge (Saphan
Pa Than). Both were severely wounded and died from the combat. The youngest
brother, Chao Sam Phraya, living in Chainat, was then proclaimed King under the title of
Boromaraja II. The King commanded two chedis built on the site where his brothers
engaged in combat. 
George Bacon recalls this incident as follows: “One curious tradition is on record, the
date of which is at the beginning of the fifteenth century. On the death of King
Intharaxa, the sixth of the dynasty, his two eldest sons, who were rulers of smaller
provinces, hastened, each one from his home, to seize their father's vacant throne.
Mounted on elephants they hastened to Ayuthia, and by strange chance arrived at
the same moment at a bridge, crossing in opposite directions. The princes were at
no loss to understand the motive each of his brother's journey. A contest ensued
upon the bridge a contest so furious and desperate that both fell, killed by each
other's hands. One result of this tragedy was to make easy the way of the youngest
and surviving brother, who, coming by an undisputed title to the throne, reigned
long and prosperously”. 
 The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) Page 15 / Source:
 Siam, the land of the white elephant - George Bacon (1893) - page 23.