▁Ph etch ab un , ▁Ch ai y aph um , ▁L op b uri , ▁Sar ab uri , ▁and ▁N akh on ▁R atch as ima ▁Provin ces , ▁Th ailand . ▁ ▁As ▁the ▁D ong ▁Ph aya ▁Y en ▁is ▁less ▁compact ▁and ▁lower ▁in ▁height ▁than ▁the ▁mountain ▁ranges ▁to ▁the ▁north ▁and ▁to ▁the ▁south , ▁the ▁first ▁roads ▁and ▁rail ro ads ▁connecting ▁the ▁region ▁of ▁Is an ▁with ▁the ▁capital ▁Bang k ok ▁were ▁built ▁across ▁these ▁mountains . ▁Before ▁the ▁construction ▁of ▁the ▁rail road ▁at ▁the ▁beginning ▁of ▁the ▁ 2 0 th ▁century , ▁communication ▁between ▁these ▁two ▁parts ▁of ▁Th ailand ▁was ▁difficult . ▁The ▁survey ▁for ▁the ▁building ▁of ▁the ▁N ort he astern ▁Line ▁of ▁the ▁State ▁Railway ▁of ▁Th ailand ▁began ▁in ▁ 1 8 8 7 . ▁ ▁Geography ▁The ▁D ong ▁Ph aya ▁Y en ▁Mountains ▁consist ▁mainly ▁of ▁a ▁range ▁of ▁scattered ▁medium - height ▁hills ▁stretch ing ▁south wards ▁of ▁the ▁Ph etch ab un ▁Mountains ▁in ▁an ▁arch ▁until ▁reaching ▁the ▁northern ▁side ▁of ▁the ▁Sank am pha eng ▁Range . ▁The ▁mountain ▁chain ▁has ▁a ▁length ▁of ▁about ▁ 1 7 0   km ▁and ▁reaches ▁a ▁maximum ▁elev ation ▁of ▁ 1 , 1 6 7 ▁m ▁at ▁Ph u ▁K hing ▁at ▁the ▁northern ▁end . ▁Other ▁pe aks ▁are ▁ 9 0 0 ▁m ▁high ▁K ha o ▁Ph ang ▁Y ai , ▁ 7 6 7 ▁m ▁high