Gen Prawit, also defence minister, said authorities have followed up the movement of the group for a long time before making the search, and uncovered the assassination plot.
He assured that Ko Tee was the one who spoke about the assassination attempt and what were found and seized was not a setup as he alleged.
Gen Prawit insisted that he was unshaken by Ko Tee’s threat and urged the news media not to give him a high profile.
Ko Tee is a hardcore red-shirt leader who became notorious over clashes with the military.
He used to lead protesters from Pathum Thani to Pattaya to surround the hotel where an ASEAN Summit was held in 2009 forcing the summit to call off immediately while many ASEAN leaders were forced to flee the angry red-shirt protesters.
He is wanted on a lese majeste charge. A warrant was issued for his arrest in April, 2014.
Mr Wuthipong is believed to be holed up in Laos and authorities are seeking his extradition for trial. He has appeared on YouTube and accused the government for setting up of the weapon seizure.