Chai (Thai: ไชย), full title in Thai Somdet Chaofa Chai (Thai: สมเด็จเจ้าฟ้าไชย) or King Sanpet VI, was a king of Ayutthaya, reigning for nine months in 1656.

Upon King Prasat Thong’s death in 1656, Chaofa Chai, his eldest son, succeeded his father as King Sanpet VI.

However, it was a Thai tradition gave brothers a higher priority over sons in succession. Prince Si Suthammaracha, Chaofa Chai's uncle, plotted with his nephew, Prince Narai, to bring Sanpet VI down. After nine months of ascension, Sanpet VI was executed following a coup. Narai and his uncle marched into the palace, and Si Suthammaracha crowned himself king. Si Suthammaracha appointed Narai as the Uparaja, or the Front Palace.

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