Coming from NK Stan.
When you hit the ring road turn left past Home Pro instead of heading straight & into the centre of town.
On the ring road, over the railway lines.
Next set (which will be the first set you get to) of traffic lights turn right. This is the set of lights before passing Global House.
Continue on this road over the railway line (again

) & the narrow part of Nong Sim Park is actually adjacent to the road you are on. But I think you need to take the first road to your left after the railway line & immediately before the park to find parking.