Syamapura Kingdom

Vaishnavism-influenced period: 4th – 8th century CE

Archaeological evidence indicates that Qiān at Si Thep developed from a prehistoric farming village approximately 2,500 years ago.^[18] During the first archaeological phase (c. 4th–5th century CE), the early settlement occupied the inner town and exhibited a burial tradition with offerings indicative of cultural interaction with India and neighboring communities in the central region and the Mun River basin to the northeast.^[19] Early Chinese textual records indicate that this polity maintained strong cultural and political ties with Southern India.^{[1]: 34 [4]} This observation is consistent with indigenous narrative traditions preserved in multiple local legends of the western Menam Valley. These traditions recount that Siddhijaya Brahmadeva, originating from Si Thep,^[c] moved to establish political authority in the area corresponding to present-day Nakhon Pathom and maintained a close relationship with the king of Lanka.^[20]: 4

According to descriptions of Qiān Zhī Fú in the New Tang Annals, which correspond to Canasapura (Jiā Luó Shě Fú, 迦逻舍佛), Tatsuo Hoshino identifies the two polities as the same kingdom during the 7th–8th centuries. He hypothesizes that Qiān Zhī Fú extended eastward into the present-day Chaiyaphum province and further into Nakhon Ratchasima province, encompassing the site at Mueang Sema [de] in the 7th century.^{[1]: 32–34} Local tradition suggests that Qiān Zhī Fú at Si Thep may have established dynastic relations with the coastal polity of Dvaravati at Kamalanka,^[22] which placed its southern neighbor, Tou Yuan, between the allied monarchs Dvaravati to the south and Qiān Zhī Fú to the north. Following the Dvaravati annexation of Tou Yuan, refounded as the Lavo Kingdom in 648, Dvaravati expanded into Qiān Zhī Fú's southeastern territory at Mueang Sema [de] during the subsequent century, prompting Qiān Zhī Fú to cede control of the Nakhon Ratchasima region and retract to its core territory in the northern Menam plain and Pasak Valley.^{[1]: 33–34} Consequently, based on Tatsuo Hoshino's theory, Si Thep served as the capital of Canasapura, while Mueang Sema [de] functioned as a regional administrative center. Thai historian Athitthan Chanklom (อธิษฐาน จันทร์กลม) similarly includes Si Thep within the Canasapura polity.^[23] Research by Karen M. Mudar also excludes Si Thep from the Dvaravati sphere.^[5]: 3–4 These interpretations are consistent with a local tradition preserved in the Legend of Phra Praton, which recounts that Dvaravati once launched an attack against Si Thep in the 7th century, overthrew the reigning monarch Manohanaraj, and carried him into captivity in Dvaravati.^[20]: 4

In the aftermath of these conflicts, the Lavo—as successor of Tou Yuan under Dvaravati—engaged in further campaigns against Chenla to the southeast. Tatsuo Hoshino suggests that multiple kingdoms participated in these conflicts,^{[1]: 54–55} including Cān Bàn and Zhū Jiāng, allied with Chenla,^[24][25] and other minor Siamese–Tai polities, including Si Thep's Qiān Zhī Fú or Gē Luó Shě Fēn, Xiū Luó Fēn, and Gān Bì, collectively commanding approximately 50,000 elite soldiers, potentially aligning with the faction offering strategic advantage.^{[1]: 54–55} Some of these engagements may have coincided with early 10th-century conflicts between Lavo and its northern Monic sister kingdom, Haripuñjaya,^{[1]: 36–37} which weakened Dvaravati^[26]: 105 and led to the eastern portion of Dvaravati being subordinated to Tambralinga and Angkor in the 10th and 11th centuries, respectively.^{[27][28]: 191}

Golden period: 8th – 10th century CE

During this period, Buddhism supplanted Vaishnavism.^[19] Concurrently, Dvaravati's influence over the Menam Valleys declined,^[29]: 60 allowing monarchs from Qiān Zhī Fú and other Tai principalities in the upper plain to gradually assimilate remaining Dvaravati entities. As noted in the Cefu Yuangui, Gē Luó Shě Fēn, a corrupted form of Si Thep's Jiā Luó Shě Fú, controlled territory west of Dvaravati,^{[1]: 38–39} granting access to maritime trade routes and contact with Srivijaya. Historical accounts record a Siamese naval expedition led by Passara, son of the king of Syam, which attempted to reach Macassar on Sulawesi but was diverted by a storm near Bali, subsequently establishing the settlement of Passaraan in Java in 800 CE.^[30]: xvi

The relocation of the political center to the western lower plain and the enthronement of Qiān Zhī Fú's new—likely Daic-speaking—dynasty at the western terminus of the trans-Mekong trade route, combined with conflicts between northern Champa and Daic-related Đại Việt at the eastern terminus, resulted in the inland Cham polity of Zhān Bó and other former confederated states in the Chi–Mun basin losing access to maritime routes and dissolving their alliance with Qiān Zhī Fú at Si Thep. These Chi-Mun polities, later associated with Yamanadvipa or Java, established the new trading polities in the area of Angkor to the south to secure maritime access through the Tonlé Sap and lower Mekong. Within a few decades, Angkor emerged as the dominant regional power, eclipsing inland kingdoms.^[7]: 93

The Pali Ratanabimbavamsa [th] or The Chronicle of the Emerald Buddha references a polity named Ayojjhapura, situated north of Lavapura.^[31]: 51 Its ruler subsequently invaded Inthapatnakhon (อินทปัตย์นคร), and acquired the Emerald Buddha.^[31]: 51 These events likely occurred in the early 10th century, after the period of the great king of Inthapatnakhon, Padumasuriyavamsa (r. 757–800). Another Pali chronicle, Jinakalamali, describes Ayojjhapura as a metropolitan center (mahā-nagara) governed by Rajadhiraj, recognized as the preeminent ruler of Rāmaññadesa.^[32]: 126 Based on these accounts, Thai scholars locate Ayojjhapura at Si Thep, the only substantial ancient settlement north of Lopburi.^[21]

Angkorian invasion: 10th – 11th century CE

Qiān at Si Thep came under the authority of the Shaivism Angkor polity in 946,^{[19][33]: 303, 308–309} as evidenced by inscriptions recording the victory of Angkorian king Rajendravarman II (r. 944–968) over Rāmaññadesa to the west.^[34]: 3546 Following this event, Qiān Zhī Fú experienced a decline in prosperity, potentially attributable to climate disruptions, epidemic crises, or alterations in Angkorian trade policies during the 12th–13th centuries. The residual population subsequently migrated to Lavo's Lavapura^[23] and to Xiān's Ayodhya.^[21] Its seat at Si Thep appears to have been abandoned by the 13th century, coinciding with the rise of Sukhothai as the new political center of the upper Menam Valley.^[35]

During the later phase of Qiān Zhī Fú at Si Thep, an early Siamese dynastic line transitioned to Yassouttora Nacoora Louang or Tasoo Nacora Louang, identified with Lavapura of Lavo. Following the loss of the eastern Menam Valley to Angkorian expansion, this dynasty temporarily relocated northward to Sukhothai/Nakhon Thai circa the 1150s. Subsequently, the monarchs shifted their focus southward to the western Menam Valley, where they consolidated control over the region as part of Xiān’s territorial domain, encompassing Suphannabhum, and undertook the reestablishment of Phrip Phri.^{[36]: 127 [37][38][39]} This region subsequently emerged as a new political and cultural power base for Xiān until the establishment of the Ayutthaya Kingdom in the mid-14th century. The Xiān regained influence over the eastern Menam Valleys at Lavo, previously lost to Angkor, around the 1280s, as indicated by records of significant Xiān settlements in Lavo,^[40][41] as well as Lavo tributes sent to China in 1289^[42] and 1299.^{[15]: 221–222}