This is a good summary, making for layman like me could understand about the complexity of Buddhism in China. In Thailand, we follow Hinnayan tradition but in practice there are still 2 distinct division, Mahanikai and Thammayut. Originally, we had only one Mahanikai until King Rama IV founded Thammayut sect while he was still in monkhood during King Rama III reign. Legend tells that Monk Monkut (his name when he was Prince) saw Mon monk's manner as solemn and seem to be stricter regarding Buddhist precepts. So he began to dress himself like Mon monk. Soon his monk followers did likewise. When Prince Mongkut ascended to the throne, Thammayut sect prospers until now as it deems as a Buddhist sect established by the Thai King. Mon ethnics used to own Hongsawadee kingdom opposite Kanchanaburi but were invaded and conquered by Tong-U kingdom (Burmese), who later also invaded Ayutthaya kingdom and Ayutthaya became a vassal state for about 2 decades before King Naresuan liberated Ayutthaya. However, Mon etnics never had a chance to revive their kingdom, living at the old city or migrated to Kanchanburi and even to Bangkok. BTW, I can't type Thai as my notebook don't have Thai alphabets.