Police teams launched raids simultaneously on various locations in an operation that ran from May 2-11, according to Naret Nanthachot, commissioner of Provincial Police Region 1.
The operation mainly targeted suspected owners of war weapons or explosive devices, as well as those with outstanding arrest warrants.
It also aimed to locate and arrest hitmen, as well as those who make homemade guns and sell via the internet.
He said that during the 10-day operation, police had confiscated 388 handguns, 253 of which were unregistered, and arrested 157 people who already had arrest warrants. They also seized three assault rifles and more than 2,300 rounds of ammunition.
More than 1,700 drug smugglers and users, mostly involved with methamphetamine pills, or ya ba, were also detained during the crackdown, he added.
The nine provinces under the jurisdiction of the Provincial Police Region 1 are Samut Prakan,Nonthaburi, Pathum Thani, Ayutthaya, Ang Thong, Chai Nat, Sing Buri, Lop Buri and Saraburi.