Phetchabun (Thai: เพชรบูรณ์, pronounced [pʰét.tɕʰā.būːn]) is one of Thailand's seventy-six provinces (changwat) and lies in lower northern Thailand. Neighbouring provinces are (from north clockwise) Loei, Khon Kaen, Chaiyaphum, Lopburi, Nakhon Sawan, Phichit and Phitsanulok.
Chaiyaphum (Thai: ชัยภูมิ, pronounced [tɕʰāj.jā.pʰūːm]; Northeastern Thai: ไซยภูมิ, pronounced [sa᷇j.jā.pʰu᷇ːm]) is one of Thailand's seventy-six provinces (changwat), located in central northeastern Thailand, also called Isan. Neighboring provinces are (from north clockwise) Khon Kaen, Nakhon Ratchasima, Lopburi, and Phetchabun.
Nakhon Ratchasima (Thai: นครราชสีมา, pronounced [ná(ʔ).kʰɔ̄ːn râːt.tɕʰā.sǐː.māː]; Northeastern Thai: นครราชสีมา, pronounced [nà(ʔ).kʰɔ̂ːn lâːt.sā.sǐː.mâː], often called Khorat (Thai: โคราช, pronounced [kʰōː.râːt]; Northeastern Thai: โคราช, pronounced [kʰôː.lâːt]) (alternate spelling Korat) is one of Thailand's seventy-six provinces (changwat) and lies in lower northeastern Thailand also called Isan. At 20,736 square kilometres (8,006 sq mi) it is the country's second largest province by area, has a population of approximately 2.6 million, and generates about 250 billion baht in GDP, the highest in Isan. Neighbouring provinces are (clockwise, from north) Chaiyaphum, Khon Kaen, Buriram, Sa Kaeo, Prachinburi, Nakhon Nayok, Saraburi, and Lopburi.
The capital of the province is the city of Nakhon Ratchasima in Mueang Nakhon Ratchasima district, also called Khorat.