Tun Sun

Tun Sun () or Tian-Sun or Tien-Sun (; ) or '''Tu-k'un/Tou-k'ouen/Ch'u-tu-k'un (), later Lang-chia or Lang-ya-hsiu''' (, ) was a group of five ancient Mon political entities, stretching from present-day lower central Thailand to the Kra Isthmus in southern Thailand and Tanintharyi Region of Myanmar. It existed from the 1st to 6th centuries CE, 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. It was also one of the earliest Indianized-states in Southeast Asia.

Tun Sun remained independent until it was seized and became a vassal of Funan in the 3rd century CE, at least before 245 CE. Tun Sun disappeared from history about the beginning of the 6th century CE, when new principalities of Dvaravati emerged in central Thailand.

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. Several scholars speculated that Lang-chia is situated in lower central Thailand, probably the same territory as Tun Sun. Lang-chia additionally sent embassies to China in 523 and 531. Cœdès proposed that ''Lang-ya-hsiu'' expanded its territory eastward to modern Chanthaburi province in eastern Thailand where it bordered with Chenla.

Southern Lang-chia later joined Pan Pan in the south, while its northern territory became Dvaravati and the colony of Lavo Kingdom after merging with Chin Lin following the decline of Funan in the mid-6th century. 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. Provided by Wikipedia