Thai Premier General Prayut Chan-o-cha said the male suspect was apprehended while trying to cross the border at Ban Pa Rai in Thailand's Aranyaprathet district in Sa Kaeo province, nearly two weeks after the attack.
"It's true. He has been arrested at Sa Kaeo checkpoint," Prayut said, adding, "We are interrogating him. He is a main suspect and a foreigner."
According to media reports, the man arrested is the one seen in CCTV footage on August 17 wearing a yellow shirt and leaving a backpack reportedly containing the bomb behind at the temple, a popular tourist attraction. However, this could not be officially confirmed.
Prayut said it would be great if the suspect is the man they are seeking. "So we will know who they are, where they came from, who's behind this."
More From This Section
"Don't say just yet it's about this and that. It could affect international affairs," he said. "We have to do a lot of tests, fingerprints. If he is the guy, he is the guy."
The Premier did not disclose the nationality of the man.
Twenty persons were killed in the blast and more than a 100 others injured.
Taskforce Major General Srisak Poonprasit was quoted by The Nation newspaper as saying the suspect was spotted by a joint patrol unit of troops and police trying to sneak across the border in Ban Dong Ngu village in Tambon Parai of Aranyaprathet district to Cambodia.
The patrol unit recognised the suspect's face as being similar to the man seen on the CCTVs, the paper said.
Thai police expanded their investigation into the attack yesterday, seizing explosives from a suburban apartment building and warning that the group they are pursuing had been preparing "quite a lot of bombs".
Thai police on Saturday arrested the first suspect in the case, an unidentified foreigner.
The arrested man was carrying a fake Turkish passport but his identity remained unclear as Turkish diplomats said they did not believe he was a Turk. Yet nearly two weeks after the attack, the authorities have remained vague on the possible motives of the perpetrators.