Phimai is easy to get to by taking a bus from the terminal 2 bus station, to the north of Khorat city centre. It takes about an hour and costs around 50 baht. Buses depart every 30 minutes between 5am and 7pm. There is no direct route to Phimai outside of Khorat and all onward travel requires that you first get back to Khorat and proceed from there.
There're 2 types of bus from Khorat to Phimai - Chumpuang.One is air-con 2nd class(white and blue colour) and ordinary bus (orange colour).Both can take at the New Bus Terminal or Bor Khor Sor Mai in Khorat city.The ticket for ordinary bus is 34 THB.The trip takes about 1 hour for Phimai.The bus stop in Phimai is close to clock tower for the arrival and you can take the bus back to Khorat at the front of Phimai Historical Park(near the stalls).