Surin city itself is compact enough to walk for those staying near the centre. Tuk-tuks are plentiful and cheap for longer trips across town or to the bus station. Negotiate a price before getting in.
For the surrounding sites, you need your own transport or a hired driver. The most practical arrangement is to rent a motorbike — several shops near the train station offer them for around 200–300 baht a day. A car with driver can be arranged through guesthouses for day trips to Prasat Sikhoraphum and Ban Ta Klang; expect to pay 800–1,500 baht for a full day depending on distance.
Shared songthaews (converted pickups) run fixed routes to nearby towns but are not useful for the main tourist sites. Minivans to larger Isan cities like Ubon Ratchathani and Korat depart from the bus terminal.