Thai police on Saturday said they have arrested a man "likely involved" with a deadly bomb attack in Bangkok last week that killed 20 people and wounded scores more.

"We have detained one person," deputy national police chief General Chaktip Chaijinda told reporters in a live televised broadcast.

"We have found components of bomb-making materials in his apartment and I am confident that he is likely involved with the bomb attack," he said on broadcaster T News.