Foreign bomb suspect arrested at Thai-Cambodia checkpoint

Thailand's prime minister said Tuesday a second foreign man has been arrested at a checkpoint on the Cambodian border on suspicion of involvement in last month's deadly shrine bombing.

It was the second confirmed arrest in connection with the August 17 blast that tore through a religious shrine in downtown Bangkok and killed 20 people, mostly ethnic Chinese devotees.

Prayut Chan-O-Cha, who also heads the nation's junta, was asked by reporters to comment on rumours a man had been detained.

"It's true. He has been arrested at Sa Kaeo checkpoint," Prayut said, referring to the Thai side of a border crossing with Cambodia.

Asked whether he is thought to be the person who planted the bomb at the Erawan shrine in Bangkok's busy Chidlom shopping district he replied: "We are interrogating. He is a main suspect and a foreigner."

The motive for the blast -- Thailand's worst single mass-casualty attack -- remains shrouded in mystery.

Suspicion has variously fallen on Thailand's bitter political rivals, organised criminal gangs, Islamist militants, rebels in the kingdom's strife-torn south and sympathisers of refugees from China's Uighur minority.

Arrest warrants have been issued for several people in connection with the blast.

The only named warrant is for a 26-year-old Thai Muslim woman called Wanna Suansan.