Police hunting for the perpetrators of Thailand's deadliest bombing arrested a suspect on Saturday they said fit the description of a man identified on security cameras as leaving a rucksack at the site of the 17 August blast in Bangkok.

Police raided an apartment used by the man in northern Bangkok on Saturday and discovered possible bomb-making materials, national police spokesman Prawut Thavornsiri said.

The suspect "looks like the one we are looking for", he said.

"They also found a lot of materials which can be used to make bombs," Prawut said.

The bomb tore through the crowded Erawan Shrine in Bangkok's commercial heart on 17 August, killing 20 people, most of them tourists, and wounding scores more.