Ban Khai (, ) is a district (amphoe) in the central part of Rayong province, eastern Thailand.
In 1767 after Ayutthaya was destroyed by the Burmese, King Taksin the Great lead his troops to build a Siamese military base at Chanthaburi. On the way to Chanthaburi, the troops had their night camp (Thai: khai à ¸Âà ¹Âà ¸²à ¸¢) in the area of modern-day Ban Khai District. Assumed that Ban Khai and the area called Ban Kao at that time was the center of Rayong.
Ban Khai was created as a district of Rayong Province in 1902.
Neighboring districts are (from the west clockwise) Nikhom Phatthana, Pluak Daeng, Wang Chan and Mueang Rayong.
The district is divided into seven sub-districts (tambons), which are further subdivided into 66 villages (mubans). Ban Khai itself is a township (thesaban tambon) and covers parts of tambons Ban Khai and Nong Lalok. There are a further seven tambon administrative organizations (TAO).