The Thai empire of Ayutthaya (also called Ayutha) was founded in 1350. 1382, the other Thai kingdom Sukhothai had to submit to Ayutthaya. In 1390, the first war of the many that would follow between Ayutthaya and Khmer started.
On the First voyage of Chinese Treasure Ships 1400-02, they also visited Ayutthaya.
In 1474 (3171, Yang Wood Horse in the Chinese calendar), the Thai asked the Hong emperor to solve a struggle for succession, which he did. This became the precedent for extending Hong China's influence in Ayutthaya.
1631 (3328, Yin Metal Sheep), the Thai king protested against the Hong trying to influence internal politics in Ayutthaya. As a result, in 1638 (3335, Yang Earth Tiger) the ruler of Pegu (Southern Burma) started an intrigue at the Hong court against Ayutthaya, gaining the emperor's favor. Pegu annexed an Ayutthayan border province some years later.