Taking a songthaew (10-15B within the downtown district) is the easiest way to travel around Nakhon Si Thammarat. The pickup trucks are scattered throughout town - just wave at one to get them to stop. The sights are very spread out along the main road that runs through the town called Rajdamneon Road, so it's best to take them in order to visit them.
Mini-busses depart for Hat Yai from Th Yommarat, which runs in front of the train station. If you walk south along this road from the station you'll come across a counter on the pavement. This saves you having to get to the bus station. It cost 140 baht and took about 3 hours with a stop for lunch along the way.
With a short 5-10 minutes walk from Thai Hotel, head to the terminal where SongTaew awaits to ferry passengers to Khiriwong Village. 25 Baht per person for going to Khiriwong Village.