Ban Chiang Hotel has wifi, but you pay extra. It isn't cheap, and you can only buy time cards for the times that they have, which may not fit your length of stay.
B&B Resort has wifi and direct line hookups in the room, but the last time I was there, the Internet connection was not reliable.
Not sure when u are coming to Udon, but within a couple of weeks I hope to have wireless ADSL up and running, no lifts but rooms on ground level and straight onto the pool.
Nice! that may be a bit far in the other direction tho. My friend lives near the Big C. Was hoping to find something near the mall maybe. What are the coordinates on the Udon Map? coming late January. thx.
KTC condotel has direct ethernet line hookups in the room. (room =400/day)
The same applies to Udon Resort where room are priced at THB 320/day,although here you can either rent the cable at 20baht from the reception, or bring your own.