Bus Terminal 2, the New Bus Station — Bor Kor Sor Mai — is situated far west of town on the outer ring road. Songthaews #10, 15 and 22 pass close to both stations and are very cheap, but you’ll need to know where to hop off as they don’t actually go into the parking lots. Tuk tuks will ask for a negotiable 150 to 200 baht to take you from one station to the other.

 

Bus Terminal 2, fares include:

Bangkok (Morchit): There are three departures from 20:45 to 21:25 for 500 baht.
Chiang Mai: There are at least six departures from 17:00 to 20:45, with fares ranging from 600 to 850 baht depending on class. The somewhat grueling ride uses winding mountain roads and takes a solid 12 hours. Also services Phitsanulok and Lampang. If you don’t want to take a night bus, catch a Phitsanulok-bound bus and make a transfer.
Chiang Rai: First-class buses depart at 15:50, 17:00 and 18:50 for 595 baht. VIP buses depart at 18:15, 20:00 and 20:45 for 700 to 1,110 baht. The ride takes 12 to 14 hours. Also services Phitsanulok, Uttaradit and Phrae.
Loei: Departs every half-hour from 04:50 to 17:50 for 100 baht and takes around three hours. Also services Nong Bua Lamphu.
Nong Khai: Minibuses pick up hourly from 05:00 to 19:00 for 50 baht.
Phitsanulok: Departs at 07:30, 09:30 and 12:00 for 225 to 300 baht depending on class, and takes around seven hours. Also services Loei, Phu Ruea National Park and Dan Sai. If heading to Sukhothai, make a transfer in P’lok.

Additionally, a handful of minibuses and long-distance songthaews depart from Rangsina Market, located on the far northern side of town off Udon Dutsadi Road. Fares from here include:

Ban Phue (closest city to Phu Phra Bat Historical Park): Minibuses depart hourly from 06:00 to 20:00 for 80 baht and take an hour.
Nong Khai: Minibuses depart every half-hour from 05:00 to 20:30 for 50 baht.
Sangkhom: Songthaews depart five times from 10:00 to 16:40 for 120 baht and take four to five hours.