The Yuan are the people of Lanna or Yonok, then an independent kingdom in the upper reaches of the Chao Phraya River basin with a capital at Chiang Mai.

It counts among only a handful of works of Thai literature from the Early Ayutthaya era that have survived, and may be still in its original form, without later revisions.

The main body of the poem consists of 1,180 lines in a variant of the khlong (Thai: โคลง) meter.

The poem is considered important as a source of historical information, as an example of poetic form and style, and as a repository of early Ayutthayan Thai language.

From the late 14th century, Lanna and Ayutthaya vied to control the Northern Cities and thus dominate the whole basin.

The accession of King Trailokanat in 1448 was a significant step in this process as he was descended from the Ayutthaya and Sukhothai ruling families on the male and female side respectively.

Soon after this accession, Phraya Yutthisathian (Thai: ยุธิษเฐียร), a prince of the Sukhothai family, rebelled against Ayutthaya and took his followers to Chiang Mai.

According to the Chiang Mai Chronicle, when Yutthisathian and Trailokanat were childhood friends in Phitsanulok, Trailokanat had promised that on becoming king he would appoint Yutthisathian as upparat or deputy king, governing the northern part of the merging domain, but reneged and made him only governor of Phitsanulok.

[3] Possibly this story is the way the chronicle conveys a wider opposition to the creeping merger among the Sukhothai nobility.

King Tilokkarat of Chiang Mai (r.1441-1487) had already greatly expanded the Lanna domain by absorbing Phrae and Nan.

Yutthisathian encouraged him extend his power over the Northern Cities, leading to a series of battles between Ayutthaya and Lanna over the next thirty years.

Although the poem presents the battle as a great victory, it did not settle the contest between Ayutthaya and Lanna over the Northern Cities which continued intermittently until the mid 16th century.

Troops from Tilokkarat's allies, Nan and Phrae, take control of Chiang Chuen, propelling many nobles and men to flee and join Trailokanat in Phitsanulok (stanzas 125-152).

Tilokkarat appoints a new ruler in Chiang Chuen, Jae Hom, who readies strong defenses with reinforcements from Lampang (stanzas 153-174).

Trailokanat readies his army at Phitsanulok, travels up the River Nan, and then marches towards Chiang Chuen (stanzas 175-201).

Yuan Phai is the only source of information that he was born in the year that his father, Borommaracha II or Sam Phraya, led an army to Angkor, which was 1431.

He composed or commissioned the Mahachat Khamluang, another early classic based on the Jataka story of Phra Vessantara.

This arrangement, in which the king along with a deputy or son occupied Ayutthaya and Phitsanulok as twin capitals was practiced intermittently from this time until the late 16th century.

There are confusing and contradictory accounts of the latter part of the reign in various sources, but the authoritative Luang Prasoet Chronicle specifies that he died in Phitsanulok in 1488.

His year of birth is unknown but the Chiang Mai Chronicle describes him and Trailokkanat as "boyhood friends"[6] so their ages may have been close.

[7] The opening stanzas of Yuan Phai are an early and important source for one of the main theories of kingship in Ayutthaya.

Brahma, Vishnu, Shiva, golden Meru's lord, great Yama, fine Maruti on his horse, Viruna, Agni, demon-chief Kuvera, the sky-illuming sun and lustrous moon;

these gods eleven joined with one resolve to make a holy Lord All-Knowing one to come, protect, sustain and feed this world.

In 1968, MC Chand Chirayu Rajani proposed that Chiang Chuen was the site now known as Si Satchanalai, although he had never visited the place.

The poem states that the town is screened by three hills, is flanked by rapids in the river and the Meng marsh on one side, and has a triple moat and laterite walls.

Yuan Phai references several characters from the Mahabharata—Karna, Arjuna, Krishna, Bhima, Duryodhana—as well as naming the Pandava and Kaurava, the two warring clans in the Indian epic.

B. Griswold and Prasert na Nagara published an article in English[14] setting the poem into its historical context, using material culled mainly from the Ayutthaya and Chiang Mai chronicles.

In 2001 the Royal Institute of Thailand produced an edition based on Chanthit's format, with many reinterpretations devised by a 19-member committee.

[1] As many words are obscure, and parts of the manuscript may have been corrupted by damage or faulty copying, the committee offered alternative readings of several lines.

The translation is featured in the Anthology of ASEAN Literatures of Thailand, Volume II a (วรรณกรรมอาเซียน ประเทศไทย เล่ม ๒ เอ), first published in 1999.