The southern gate to the park seems closer to Bangkok but as there is no direct expressway, less accommodation choice and the park headquarters being very far from the south entrance, most people use the Pak Chong area as transit place to visit Khao Yai park. It’s also the most popular with Thai residents for all the attractions around.
By minivan: Direct minivans leaves to Pak Chong from Victory Monument minivan station
Direction of Victory minivan station: it is located under the expressway bridge crossing Phahon Yothin Rd., 100 meters north of the Victory square, cross the square by the footpath from BTS station up to Phohon Yothin road, (there’s a Mc Donald at the corner). Minivans leaves every 2 hours for about 180 Thb per seat, ask where to queue as there is no English sign on the boards. Minivan is a first arrived, first served service, so check how many people are in front of you to make sure you get in ( generally 10/12 person can fit in) you pay your fee to the driver.
During concert season in winter, most music festival organize minivans shuttles as frequently as every half hour to either Bonanza or Greenery area in Mu Si from Victory monument.
BTS: Victory Monument
Many resorts can organize a private minivan to pick you up from your hotel in Bangkok by minivan for about 3500 Thb per way for up to 8 people. Local travel agency in the Khao San area have some minivans going there too once a day or you can charter your own.
By bus: buses leaves every half hour or so from Mo-Chit north terminal in Bangkok (about 180 Thb). Pak Chong is on the way to Nakhon Ratchassima / Korat, which is the main transit road to Isaan province, so you are sure to always catch a bus easily, just make sure the bus stop in Pak Chong. From Pak Chong, songthaew runs every half hour along Thanarad rd. up the park entrance. http://www.mochit.com (in Thai)
By train: trains leaves Hualampong station 4 times a day but takes from 4 to 5 hours so it s probably not the best way to get there from Bangkok.
By road/ car from Bangkok center:
-Head north east towards Saraburi / Nakhon Ratchassima by taking the Phahon Yothin Rd., the expressway along The Dong Muang Airport in Bangkok
-Before Ayutthaya, head north east towards Saraburi.
From Eastern Bangkok and the Suvarnabhumi international airport, take the outer ring road up to Phatum Thani to catch the Mittraphap Road leading to Saraburi.
-Just before Saraburi, continue the Mittraphap Expressway leading to Nakhon Ratchassima up to Pak Chong, about 45 km from Saraburi.
– From Pak Chong, The national park is at the end of Thanarad rd., south of Pak Chong town. The park entrance is about 20 km from the expressway exit, park headquarters are located about 10 km south from the park entrance.
FROM KORAT/ NAKHON RATCHASSIMA
By bus: Buses runs every half hour from Korat bus station towards Bangkok and stop in Pak Chong.
Getting around in Khao Yai: Songthaew runs permanently along Thanarad rd. up the park entrance.
A good option is to rent a motorbike to be able to visit the area at your own pace, bicycle are also available for rent, be aware that once you pass the park gate the park road is mountainous up to the park headquarter. Mountain bike are allowed in the park. Outside the park, there is plenty of nice bicycle Roads threw vineyards and the country. Check futures posts about that.