Acting national police chief Watcharapol Prasarnratchakij said 21,950 of the guns melted down were handguns and 12,400 rifles.
Pol Gen Watcharapol said the seized weapons were put in 88 crates and delivered to a foundry in Phra Pradaeng district of Samut Prakarn province, where they were destroyed.
He said the melting process would take the whole night and weapons were expected to produce about 30 tons of iron, which would be reproduced as iron rods to be donated to temples for construction purposes.
Pol Gen Watcharapol said the regulation governing destruction of seized guns may be amended to empower provincial or regional police chiefs to destroy weapons once a year. He said keeping large numbers of seized guns for a long time is costly.
The weapons destroyed were old and not usable. Those seized after the imposition of martial law have not been destroyed because the cases have not yet been finalised, he said.