Khao Yai is easily accessible by car. Take the Pak Chong or Prachinburi routes from Bangkok.
Prachinburi route: take highway No. 305 from Rangsit-Ongkharak road to Nakhon Nayok and follow highway number 33, then turn left at Naresuan ring road and follow highway No. 3077 and after about 10 km you’ll reach the park headquarters. This route is a shorter distance from Bangkok but steeper. This route is also more scenic and has many points of interest. Heaw Narok waterfall is a short distance if you take this route.
Pak Chong route: Follow highway No. 1 to Saraburi province, then turn right to route No. 2 which goes to Pak Chong. Then take highway No 2090 for about 20 kilometres and you’ll reach the entrance. The Pak Chong route is longer.