At a press conference at the Metropolitan Police Bureau on Friday, deputy police chief Pol Gen Somyot Poompanmoung said Narongsak Phlai-aram, 31, was arrested at Suk Sabai Apartment in Talad Khwan sub-district of Muang Nonthaburi district, Nonthaburi, about 8pm on Thursday.
The deputy police chief said Mr Narongsak had confessed he had used an M79 grenade launcher to fire grenades at PDRC demonstrators near Shinawatra 3 Tower on Vibhavadi Rangsit Road in Chatuchak district, Bangkok, about 4.25pm on March 7, 2014, and on Sawankhalok Road in Dusit district, Bangkok, about 1pm on March 29, 2014.
He also admitted firing grenades at the head office of the National Anti-Corruption Commission in Nonthaburi about 10pm on March 27, 2014.
Pol Maj Gen Amnuay Nimmano of the Metropolitan Police Bureau said Mr Narongsak admitted receiving the grenade launcher from another man in front of the Imperial department store on Lat Phrao Road, Bangkok, and said he had been paid 3,000-4,000 baht for each attack.
There would be more arrests for similar offences soon, Pol Maj Gen Amnuay said.
In another operation, police seized many weapons at room 402/24 of Building 14 of Srithai Condominium on Pracha Uthit 33 Road in Thung Kru district on Thursday.
They found two rocket-propelled grenade launchers, three RPGs, 13 RGD-5 grenades, an AK assault rifle, 11 rounds of 40mm ammunition, 127 7.62mm bullets, 18 11mm bullets and a bullet-proof vest, police said.
Pol Gen Somyot and Pol Maj Gen Amnuay both said the weapons were connected with the violent incidents against PDRC demonstrators and also with protests in 2010.
The room belongs to Thanainant Termjitcharoen, who had leased it to another person.