Stop for lunch on the drive up to Chiengmai( 700 kilometers) at PTT gas station past Nakorn Sawan. Excellent Thai lunch for 4 persons including Pepsi is $6. My favorite is "Namprik Pla Tu and Cha-om". One must select gas station near small town with only one food outlet for good food. Large gas station with lots of food outlets cater to tour and bus traffic and usually not very good.