Published: 2017-03-19 20:49:25 BdST
It is the latest discovery of a weapons stockpile belonging to a member of the red shirt movement, a political group loyal to exiled prime minister Thaksin Shinawatra.
Police on Saturday found dozens of rifles and grenades, and thousands of rounds of ammunition, at a house belonging to red shirt leader Wuthipong Kochathamakun, who has been on the run since the military coup.
Police also arrested nine men in connection with the arms seizure, saying they had clear evidence the suspects and their extended network were aiming to cause unrest.
"We found a rifle with a scope. We guarantee that this is not to shoot at birds but was going to be used to assassinate the leader of the country," National Police Chief Jakthip Chaijinda told reporters on Sunday, referring to Prime Minister Prayuth Chan-ocha.
Prayuth, then the army chief, overthrew the government of Thaksin's sister Yingluck in a 2014 coup.
His junta discovered dozens of weapon caches belonging to groups they said were loyal to the Shinawatra clan.
The junta said the stockpiles showed there were groups trying to create instability and justified their seizure of power.
Police chief Jakthip presented no other evidence of an assassination plot, but said Wuthipong and his network had always opposed the junta and the group had predicted on social media that the prime minister would be killed.
Police said the group was planning an ambush if officials had continued their operations against a influential nearby Buddhist temple, which is seen as having close ties to Thaksin.
Thai police ended their search of the Dhammakaya temple earlier this month after laying siege to it for more than three weeks without finding the former abbot, who is wanted for suspected money-laundering.