Wow! You’re crazy! That road is very dangerous and full of cars. I have never been there but I had read and heard so much about it!
Next time try the Isann route, along the Khong River, it’s less strenuous! But on the way up to Leoi and Chiangkarn could be demanding.
Last month I met an English couple cycling along the dirt road, being lost!! They shouldn’t depend on google map too much. They only had the photo of the resort they were looking for! So, I advised them to stick to the main road as it would be easier to find cheap guest houses. The sky was getting dark so I suggested the local resort. But there were no cheaper rooms left. It seemed they didn’t do enough research on the route they were taking.
It seemed they had no choice but to get closer to town area for accommodation.
If you had been cycling for 14 years! You have to know Thailand countryside better than me!
Yes, too many cars but it felt annoying rather than dangerous as the traffic was all going slowly. The Khong river is mentioned when we talk about where to go next so I guess we'll do it sometime - thanks for the suggestion. For us, the back roads are always the most interesting - both of us being reasonable at speaking Thai helps a lot!