Phu Foilom (Near Udon) :
now here we are talking about my backyard . Living near Nong Wua So , I am all the time up and about those mountains with my bike . There were 2 access roads discribed earlier in this thread . Here is a third one: In Nong Wua So you turn left at the red ligth towards Amphur Nong Wau So . At KM 6 ,you turn left on a sand road (Sign ) ,which is not very good ,I must say ) ,after about 10 km one reaches a village (sorry forgot the name P.... something ) ,through the village ,turn left ,up to near a big Wat ,turn rigth (sign) and follow the road for another 15 km or so . You come to Phu Foilom from the Western approach. This ride is a bit trikky at times . Small motos can do it ,better than chopper type bikes ,but have done that too . Offroad bikes or pickups have no problems.
One drives trough rubber plantations and finally near the summit ot the mountain range through extended forrest plantations , very nice and recommendable . I do this drive at least once a month.Bonus is ,that there are restaurants up there with beer etc ,to give you something to look forward to whilst driving . Also one can rent tents and sleeping bags cheaply up there . However do not go on a weekend ,unless you plan on sharing the place with hundreds of partying teenagers. During the week the place is mostly deserted.