Ouachita National Forest, Kiamichi Ranger District, 6 miles east of Big Cedar, OK (junction of US 259 and OK 63) on OK 63. Turn left onto NF 6032.
There a several places to pull in and park a car (even a small RV), between the road and the Kiamichi River. The river is always running so you could filter water. It’s also very scenic.
Haven’t camped here myself but parked here for backpacking. Nearest town with amenities is Mena, AR, another 20 miles east.