Among the haul were four .38 pistols, a 9mm gun, an 11mm pistol and a shotgun, said Pol Col Akkrawut Limrat, the CSD officer leading the raid.
Police also found more than 500 rounds of ammunition for several guns, two smoke grenades and magazines for an AK47 rifle and a carbine, he added.
The raid was the culmination of an investigation into reports that several kinds of weapons were being kept at the houses belonging to Chaiyaporn Theemasatit.
Police descended on the two buildings after receiving a search warrant from Thon Buri court, but were surprised by the extent of the weaponry they found.
Mr Chaiyaporn, who was taken for questioning at CSD head office, said he owns a seafood shop but that he, his younger brother and sister-in-law are avid weapon collectors.
The ''collection'' at the house belonged to all three, he said.
The weapons were usually kept in the house and he carried one for self-defence occasionally, despite having no enemies, he said.
According to Mr Chaiyaporn, the items found in the two houses were bought from retired soldiers or Provincial Administration Department officials and are all legally registered.
But police have charged the man with possessing unauthorised weapons.
CSD Pol Lt Col Thanin Inthaport said police will trace the origins of all weapons found in the houses and could file more charges against him.