They were also each ordered to pay a Bt90 fine.
The explosion in front of a salon caused seven injuries and damaged about 10 nearby shops.
The Corrections Department yesterday brought Narathiwat native Idris Satapo and three Pattani men, Affahum Sa-ah, Kampee Lateh and Ilroheng Waemae, to hear the ruling.
The court found them guilty of attempted murder, causing an explosion to endanger others and their property, illegally having explosive devices in their possession, and carrying such devices to a public place without sound reasons.
They were initially handed life sentences but because of their useful confessions, the terms were reduced to 66 years and eight months.