Thailand's military court has issued an arrest warrant for the spokesman of an anti-coup group over alleged arms offences, an accusation firmly rejected by the former minister.

The warrant against Jakrapob Penkair, a prominent member of the "Red Shirt" movement affiliated to the government ousted by the military in May, follows the launch of an opposition alliance to counter the junta.

The "Organisation of Free Thais for Human Rights and Democracy" (FT-HD) has vowed to press for the restoration of democratic rule from an as yet undisclosed Western country as attempts to take on the regime within Thailand are stifled.

"The military court Friday night issued arrest warrants for four people, including Jakrapob, for links with war weapons seized in Thailand during the past month," deputy national police chief Somyot Poompanmoung told AFP on Sunday.

Thailand's military rulers justified their takeover as necessary to restore peace after months of often-violent protests between pro- and anti- government factions, and had warned they would crack down on armed groups in the run-up to the May 22 coup.

Jakrapob, also once a spokesman for the government of tycoon-turned-populist premier Thaksin Shinawatra -- who was deposed in a previous coup in 2006 -- sharply rejected the allegations against him.

"There is simply no evidence whatsoever to connect me to the junta's seizure of arms and I would challenge them to produce such evidence," Jakrapob said in a statement released Saturday.

"I have no involvement in any kind of 'armed' struggle. I believe fully in a political, social and cultural struggle secured in reality by the democratic will of the Thai people," the FT-HD spokesman said.

On Sunday Thai authorities displayed rifles, grenades and bullet-proof vests collected in raids during a press conference at the army headquarters in Bangkok.

A total of 1,996 guns, 31,840 rounds of ammunition and 256 explosive devices were seized between 22 May and 25 June in operations which also led to the arrest of 38 people, said Thailand's Peace and Order Maintaining Task Force in a statement.

The majority of the arms seized were handed in by people in the central and northeast provinces after a military call for illegal weapons, according to junta spokesman Werachon Sukondhapatipak.

"The weapons have been linked with plans to instigate violence in northeast Thailand, particularly in the city of Khon Kaen," he said, without providing any more details.

The Thai coup follows years of political divisions between billionaire Thaksin, who lives in self-exile in Dubai to avoid jail for a corruption conviction, and his supporters, and a royalist establishment backed by parts of the military and judiciary.