Next place. In Nong Khai province, near the Mekong.
Road https://www.openstreetmap.org/way/287851890/history is completely inside Nong Khai province, no centimeter is in Udon Thani province. None the less, it’s ref number was “อด.5028”, i.e. containing the abbreviation for Udon Thani.
The situation on ground is not great either: at its beginning, there is a DRR sign showing “นค.5028” (i.e. the abbreviation for Nong Khai province), followed by a DRR sign with “นค.3028”. And the milestones used of them, I don’t remember which one.
Nowhere the abbreviation of Udon Thani was used.