The Hindu shrine, and the busy Ratchaprasong junction where it is located, were crowded when the explosion occurred
Mr Wongsuwon told reporters that the bombers had "targeted foreigners... to damage tourism and the economy".
"We will hunt them down," Reuters quoted him as saying.
Prime Minister Prayuth Chan-ocha said the government was setting up a "war room" to co-ordinate its response, according to the Nation TV channel.