The Sukhothai Kingdom was a post-classical Siamese kingdom (maṇḍala) in Mainland Southeast Asia surrounding the ancient capital city of Sukhothai in present-day north-central Thailand. It evolved from a trading hub to a city-state in 1127 sukha () and udaya () in the corruption form of the Sanskrit and Hindi terms Sukhodaya (), Sukhada (), and is explained as "The Happy Thai." before the later term Sukhothai applied in central Siam and also pronounced by the Mon-Khmer people occupying its territory at that period as Sakkadéa
History
Early period
thumb|Roy de Sukhodaya (Kingdom of Sukhothai) on Indochina Political Map 960 AD
thumb|Wat Si Sawai at the Sukhothai Historical Park
Borihan Thepthani claimed the city of Sukhothai was founded in 494 CE, followed by its twin city of Chaliang (). In contrast, the Legend of the Arhat (Tamnan Nithan Phra Arahant; ) says Sukhothai was founded in 679 CE by Indrajayadhirāja (), who was from the city of Nakhon Luang (; ; potentially Lavapura); however, he, in 687, was deposed by Balidhiraja, the elder son of Kalavarnadisharaja of Lavo. The succession of rulers following Balidhiraja remains obscure in the extant historical record. and has been identified with Pra Poat honne Sourittep pennaratui sonanne bopitra, whose reign is conventionally dated to 757–800 CE. This claim accords with Tatsuo Hoshino's interpretation of the Cefu Yuangui and the Book of Tang, which record that the territory of Qiān—centered at Si Thep—bordered north to Duō Mó Cháng (), a polity that Hoshino identifies as being located in the Yom and Nan river basins within the mountainous region of present-day northern Thailand. whose reign is reported to have lasted from 867 to 913 CE. This chronological positioning makes it implausible that Suvarṇakōmakam could have conducted an incursion into Sukhothai during the 9th century. Taken together, these inconsistencies substantially undermine the credibility of the abandonment hypothesis.
Following the fall of Menam polities as a consequence of Tambralinga and Angkorian incursions of the 10th century, Sukhothai is reported to have been taken over in 957 by the Mon monarch Abhayakāminī, who purportedly fled from Haripuñjaya after its capital was captured by another Khom polity, Umoṅkaselā (), situated in what is now Fang. a condition that appears to have persisted until the formal establishment of the Sukhothai Kingdom in 1238. Prior to the rise of Sukhothai, various other Tai kingdoms existed in the neighboring northern highlands. These include Ngoenyang of the Northern Thai people (present-day Chiang Saen) and Chiang Hung of the Tai Lue people (present-day Jinghong, China). According to semi-legendary Shan documents, the Mau Shan Prince, Sam Lung-pha of Mogaung, before he established the Tai kingdom of the Ahom in Assam in 1229, raided the Menam valley and the Malay peninsula as far as Tawi (Dawei) and Yansaleng (Junk Ceylon?). This purported influx of armed Tai may have had something to do with establishing the Tai kingdom of Sukhothai.
However, according to the local textual tradition, a dynastic affiliation between the Mon monarchs of the Menam Basin and the Tai nobles of the northern valleys is recorded to have been established at an earlier period, specifically during the late 7th century.
thumb|Ancient Thais (clothing and hairstyle) in the Sukhothai era found on the Wat Si Chum stone.
The following individuals are recognized as the rulers of Sukhothai preceding the formal foundation of the Sukhothai Kingdom, which earlier historians have conventionally assigned to the year 1238 CE.
{| class="wikitable" style="font-size: 95%;"
|-
!colspan=2|Ruler!!rowspan=2|Reign
|-
!Romanized name!!Thai name
|-
!colspan=3
|-
|Indrajayadhirāja||Late 8th – 957
|-
!colspan=3
|-
|Abhayakāminī||อภัยคามินี|| 957 || ไสยรังคราช||1138–?
|-
| Pra Poa Noome Thele Seri||พนมทะเลศรี||1155?–1156/57
|-
| Suryaraja ||สุริยราชา||1156–1184
|-
!colspan=3
|-
| Candraraja||จันทราชา||1184–1214|| ผาเมือง ||
|-
| Sri Naw Nam Thom||พ่อขุนศรีนาวนำถุม||1219–?
|-
| Khom Sabat Khlon Lamphong||ขอมสบาดโขลญลำพง||?–1238
|-
| Pha Mueang|| ผาเมือง || 1238
|-
|colspan=3
|}
;Notes
Kingdom establishment
Early political landscape and Monic domination
Following the fall of Lavo to Tambralinga in 927, and of Rāmaññadesa (; potentially the eastern Menam valley) to Angkor in 946, the upper Menam valley—particularly the regions of Sukhothai, Si Satchanalai, and (also known as Phichai Chiang Mai )—was brought under the control of a Monic dynasty from Haripuñjaya led by Abhayakamini from the 950s onward, as recorded in the Northern Chronicle.
Expansion of early Siamese polities
During the mid-12th century, the upper Menam Valley was likely brought under the dominion of an emergent line of early Siamese monarchs, whose principal seat of authority was situated in the Phraek Si Racha region. According to historical records, two princes from this lineage established their respective domains in the upper valley. Suryaraja, the grandfather of Si Intharathit, is recorded in the Ayutthaya Testimonies to have established his seat at Vicitraprakāra (; modern Kamphaeng Phet) around 1157. based on interpretations of the text preserved in the Dong Mè Nang Mưo’ng Inscription (K. 766), dated 1167 CE; however, he appears to have lost control of all territories in the lower Menam Valley to the monarch of Chen Li Fu and Angkorian Mahidharapura dynasty by around the 1180s to 1190s,