[4]: 25, 27 [5]: 38  It existed from the 1st to 6th centuries CE,[4]: 28 [2]: 259  and was said to have stretched from the east to the west coast, controlling a vital branch of long-distance maritime trade between the India Ocean and the South China Sea.

[7]: 234 [8] The Kingdom of Lang-chia or Lang-ya-hsiu was probably the succeeding state of Tun Sun since its first embassy, sent to China in 515 CE, claimed that the country was founded around 400 years earlier but gained independence at the end of the 5th century.

[2]: 268–270, 281  Previously, Lang-ya-hsiu was expected to be Langkasuka but according to the location provided in the Chinese text written in 636, it would be situated at the modern lower central Thailand.

[10]: 124  It also incidentally corresponded with the legendary state of Suvarnabhumi, claimed by Thai scholars to exist from the late 2nd century BCE to 2nd century CE in modern central Thailand, which consists of five king cities in the upper Malaysian peninsula, including Suvarnabhumi (the present-day old town of Nakhon Pathom), Ratchaburi, Mueang Sing, Phetchaburi, and Tanintharyi, probably with another crown dependency, Lamphakappa Nakhon (ลัมภกัปปะนคร, present-day Lampang) in the north.

[4]: 26 Roland Braddell proposed that Tun Sun was rather less than one-quarter of the distance from Chü-li, which Braddell believed to be Kou-chih of Kole polis in present-day near Kuantan of Malaysia to Funan according to the text given in Lo yang chia lan chi about the Bodhibhadra's voyage states that Tun Sun was some thirty days' sail from Funan and eleven days northwards from Kou-chih.

[4]: 26–27  This corresponded with a Thai scholar Ruangyot Jantrakiri (เรืองยศ จันทรคีรี) who said Tun Sun was founded in 52 CE and was situated in the present-day Na Tham sub-district (ตำบลหน้าถ้ำ), Yala province, in deep south Thailand.

This caused Paul Wheatley to speculated that Lang-ya-xiu was Langkasuka (Chinese: 凌牙斯加/龍牙犀角; Ling-ya-si-jia/Long-ya-xi-jiao), which was located in modern-day deep south Thailand,[13] and his assumption has been continued by many scholars to the present day.

[4]: 21 [2]: 261  It was mentioned in the 3rd century CE in the Nan-chou I-wu Chinh, a Chinese in which it is noted that the people of Tun Sun practiced intermarriage with Brahmans from India who were, reportedly, very pious.

[4] The Liáng Shū relates a story of an Indian named Kaundinya visiting Tun Sun and receiving a divine message that he was to rule Funan and went on to do so.