If you want to trip to Loei from Pattaya by bus, you can use bus operators which have route to Loei from Pattaya are as folloiwngs;
Nakhonchai Khonsong ::The bus terminal is located near three way intersection of Sukhumvit Road and Pattaya Klang (Central) Road. It is located opposite side of Nakhonchai Air at Sukhumvit Road. (Nakhonchai Khonsong is different bus operator from Nakhonchai Air.)
>> Go to Nakhonchai Khonsong