There are not many buses around town the occasional one around the 2 main roads. The main transport is songthaew and tuk-tuk.
By Songthaew
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.
Yellow - from/to the train and bus stations, down the main road of Sri Sothorn
White - from the main city market towards Bang Kaew district
Blue - from the road in front of Wat Sothorn to the city market and beyond?
Red - from the market, across the river and to Don Thong school area in peak times, and beyond at other times
Orange - from the market, across the river and down the highway
By Tuk-Tuk
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.