Three men were separately arrested in Yala and Bangkok for allegedly selling a blank gun and ammunition to a 14-year-old boy who went on a shooting rampage inside Siam Paragon shopping mall in Bangkok on Tuesday afternoon.
The incident left two foreigners dead and five others wounded.
Polce arrested two of the three suspects at a house in Yala at around 1am on Thursday.
Seized from the house were 209 rounds of ammunition for blank guns, 33 metal parts, nine magazines and other items. The two men were being taken to Bangkok for questioning.
The third suspect was arrested in Bangkok.
An investigation found that the three suspects allegedly sold a blank gun to the teenage boy who carried out the shooting. The gun was modified.
The shooter bought the blank gun online for 16,000 baht.
Chaos erupted at Siam Paragon on Tuesday, with hundreds fleeing as gunshots rang out. The dead were two women from China and Myanmar.
The teenager was arrested late on Tuesday shortly after the rampage.
