A 1st class bus service connects Chachoengsao directly with Suvarnabhumi Airport (the new BKK).
A variety of bus services run between Chachoengsao and both the Eastern Bus Terminal (Ekamai) and the Northern Bus Terminal (Moh Chit) in Bangkok.
Various express and regular trains (including two daily air-con services) leave from Bangkok's Hualamphong station. The regular (3rd class, no air-con) peak hour trains can get extremely crowded, and tickets for these services do not guarantee a seat, so arrive early to avoid having to stand.
There are not many buses around town (the occasional one around the 2 main roads). The main transport is songthaew and tuk-tuk.
These are covered pick-up trucks with two benches in the back, and indeed the name means "two benches" in Thai. Seen everywhere, to board one just put your arm out and look at the driver, who will stop. Ring the buzzer (located in the roof) to stop anywhere on the route. There is at least one section near the market that they can't stop, so be patient. The driver will pull over, let you out, and then you pay him from the passenger window. Price as of 2007 is 5 baht for students and 7 baht for adults (any distance in one direction).
The different lines are colour-coded; most start/end or at least pass through the main city market area.
The guys are genuinely nice. There's no over-charging, no taking you to see any attraction - only genuine transport. Tuk-tuks hang out at the bus/train stations, the 2 main supermarkets in town and the city market area. They can also be hailed from anywhere along the streets. You need to know basic Thai directions (turn left/right) and/or have your destination written or spoken in Thai, but they are very friendly with foreigners attempting to communicate. Basic fare will at 30 baht and usually go no higher than 50 baht (unless the distance is extremely long or a stop-over or return trip).
The main city market runs every day with raw and cooked food, clothes and basic needs.
There is a Thursday afternoon/night market which is very popular with the locals. Taking the blue songthaew (out of town) from in front of Wat Sothorn, it's about 300-500 metres. You won't see much of the market from the road as it's down a side street (to the right). You may see an ornate wood lace carving shop on the right.