Police have given their most detailed explanation yet of who they believe was behind last month's deadly bombing in Bangkok, for the first time publicly linking one of the suspects to previous explosions.

Authorities have said they believe the Aug. 17 bombing, which killed 20 people and injured more than 120, was carried out by a people smuggling gang seeking revenge for having their operation curbed.

While a presentation to the media Monday mostly summed up information released in recent days, National Police Chief Somyot Poomphanmuang said that two different groups may have been involved, and that a Thai suspect still at large had been tied to bombings in 2010 and 2014.

The 2010 bombing was loosely linked to "Red Shirt" activists who earlier that year staged militant anti-government protests.