Suphannabhum or Suvarnabhumi; later known as Suphan Buri (Thai: สุพรรณภูมิ or สุพรรณบุรี) was a Siamese city-state, that emerged in the early "Siam proper" which stretched from present-day west central Thailand to the north of the Kra Isthmus, with key historical sites at Uthong,[2]: 4–6  Nakhon Pathom,[3]: 140 [4] Suphan Buri,[5]: 40  and Ban Don Ta Phet [th].

[14]: 300, 302, 306–307  Since the river leading to the sea was dried up in places, shallow, and consequently not navigable, and also due to some pandemics, Uthong lost its influence as the trading hub; the city was then abandoned around the 11th century and the people then moved to resettle in the present day Suphanburi.

[15]: 12–3 Paul Wheatley suggests that the city-state of Chin Lin which was mentioned in the Chinese archives of the Liang dynasty as the state that was Fan Man, the Great King of Funan Kingdom, attempt to conquer in the 4th century CE, might be located in west central Thailand, since the word "Chin Lin" 金鄰/金邻 means "Land of Gold" or "Suvarnabhumi"; as mentioned in the archive, it was a state located approximately 2,000 li (800 kilometers) west of the Funan Kingdom, which corresponded to the area where is now central Thailand.

[27]: 18 After the end of the ancient maritime-oriented port era and the decline of Dvaravati, Suphannabhum then emerged around the mid-12th century following the prosperity of Lavo Kingdom and the Ankorian during the reign of Jayavarman VII and the influx of people from the north.

[7]: 276–7  This has been supported by several ancient ruins in the area that dates before the Ayutthaya period;[28]: 4  two of them are the Ankorian Bayon style and the other two are the Indian Pala-Sena architects, which are also found in Lavo, Pagan, and Haripuñjaya.

[23]: 60 Suphannabhum gradually controlled the economy of all Tha Chin Rivers and raised its power until being annexed to the Sukhothai Kingdom in 1283, as recorded in the Ram Khamhaeng Inscription.

[29] Via Royal intermarriage, Suphannabhum united with the eastern neighboring Lavo Kingdom, to establish a confederated polity seat in Ayodhya in 1351.

[39] The early era of the Suphannabhum dynasty and its relations with other royal families in the lower Chao Phraya Valley from the 10th century to the formation of the Ayutthaya Kingdom is shown below.