If you want to trip to Udon Thani from Pattaya by bus, you can use bus operators which have route to Udon Thani from Pattaya are as folloiwngs;
407 Pattana : The bus terminal is located in Gas stand at Sukhumvit Road, close to three way intersection of Sukhumvit Road and Pattaya Klang (Central) Road.
>> Go to 407 Pattana