Funnily enough that looks like a similar route (but in the other direction) I have planned for an upcoming trip.
Phayao 1202, 1426, 4005, 1020, 4015, 1174, 4017 and 1233 into Chiang Rai.
We are coming from Nan via the 1148 & 1021, so Phayao for lunch (place next door to Cupcake) and then if we are running late can do the exact reverse of yours.
Looking forward to the new map as well.