The religion of Dvaravati is thought to be Theravada Buddhism through contacts with Sri Lanka, with the ruling class also participating in Hindu rites. Dvaravati art, including the Buddha sculptures and stupas, showed strong similarities to those of the Gupta Empire of India. The eastern parts of the Chao Phraya valley were subjected to a more Khmer and Hindu influence as the inscriptions are found in Khmer and Sanskrit. Dvaravati was a network of city-states paying tribute to more powerful ones according to the mandala political model. Dvaravati culture expanded into Isan as well as south as far as the Kra Isthmus. The culture lost power around the tenth century when they submitted to the more unified Lavo-Khmer polity. Around the tenth century, the city-states of Dvaravati merged into two mandalas, the Lavo (modern Lopburi) and the Suvarnabhumi (modern Suphan Buri). According to a legend in the Northern Chronicles, in 903, a king of Tambralinga invaded and took Lavo and installed a Malay prince on the Lavo throne. The Malay prince was married to a Khmer princess who had fled an Angkorian dynastic bloodbath. The son of the couple contested the Khmer throne and became Suryavarman I, thus bringing Lavo under Khmer domination through the marital union. Suryavarman I also expanded into the Khorat Plateau (later styled "Isan"), constructing many temples. Suryavarman, however, had no male heirs and again Lavo was independent. After the death of King Narai of Lavo, however, Lavo was plunged into bloody civil war and the Khmer under Suryavarman II took advantage by invading Lavo and installing his son as the King of Lavo. The repeated but discontinued Khmer domination eventually Khmerized Lavo. Lavo was transformed from a Theravadin Mon Dvaravati city into a Hindu Khmer one. Lavo became the entrepôt of Khmer culture and power of the Chao Phraya river basin. The bas-relief at Angkor Wat shows a Lavo army as one of the subordinates to Angkor. One interesting note is that a Tai army was shown as a part of Lavo army, a century before the establishment of the "Sukhothai Kingdom". Southern Thailand Below the Kra Isthmus was the place of Malay civilisations. Primordial Malay kingdoms are described as tributaries to Funan by second-century Chinese sources, though most of them proved to be tribal organisations instead of full-fledged kingdoms. From the sixth century on, two major mandalas ruled southern Thailand, the Kanduli and the