Choose the bus company called "Air Muang Lei" (In Thai: แอร์เมืองเลย), Ticket Booth #6-7 at Morchit, Tel: 02-9360142. Get off at "Amphor Keng Krow, Chaiyaphum." (แก้งคร้อ ชัยภูมิ). The bus leaves every hour from 6.00 to 22.30. The ticket costs 310 Baht. It takes 6 hours.
From Keng Krow, you may take a motorcycle taxi to Wat Pa Sukato, Tha Mafai Wan. It should cost 200 Baht (day) and 250 Baht (night). Motorcycle taxi drivers wear bright-color vests and they are near where the bus drops you off. About 30 minutes to Sukato.