The man, whose name was not been released, was intercepted at an immigration checkpoint on Thursday.
He told police that he had lived with his family in nearby Khon Kaen.
“After questioning the man, we freed him as nothing linked him to the explosions,” said national police chief General Chakthip Chaichinda Friday.
Chakthip said a suspect in the case, Aod Payoongwong, or Yongyuth Pokkaew, was still at large possibly because of his knowledge obtained from having criminal background.