My Thai friend Bom took me to his favourite noodle house which he claims only serves very authentic Northern Thai style noodles.
Directions. Which is important because it doesn't have an English name. It is directly across the street from the Watson's at Union Mall (the aquamarine band peeking at us from where we were seated inside the restaurant). Look out for this lantern in front of the restaurant :
Because we had only two stomachs between us, we ordered one type of noodle each from a rather impressive list of noodles. As befitting Northern Thai cuisine, the flavour of these noodles seem stronger and go deeper, if it makes any sense.
The place is small, unpretentious and very casual. If I recall correctly, the two bowls of noodles and two drinks we had costed around 300 Baht.