Surawong Boonnak, 56, a village police volunteer, told Khannayao police that cycling for exercise along a frontage road beside the out-bound Kanchanapisek ring road at kolometre marker 38 on Thursday morning when he noticed five fertiliser bags containing some items left on one side of the road.
He then saw a gun barrel protruding from one of the bags.
Explosive Ordnance Disposal and forensic police went to the spot and recovered the bags.
Found in them were two RPG launchers, five RPG grenades, two AK47 rifles, eight AK ammunition magazines, 200 rounds of AK ammunition, 25 RGD6 hand grenades and two rifle stocks.
Pol Gen Ake Angsananont, a deputy national police chief, said the weapons and ammunition were believed to have been dumped there after the National Council for Peace and Order (NCPO) issued an announcement warning those possessing war weapons to turn them in to the authorities or face tough legal action when caught.