"It will be difficult to implicate him" in major corruption cases, General Sonthi Boonyaratglin told the Nation newspaper.

Investigators have failed to uncover solid evidence to support corruption charges against Thailand's ousted prime minister Thaksin Shinawatra, General Sonthi Boonyaratglin, seen here, the nation's coup leader said in an interview. [AFP]

"We cannot impound the money he made with accountable legal evidence, but can only look for some possible hidden (evidence) with questionable background," he said, but warned Thaksin not to try to return just yet.

In the past, Sonthi has justified the bloodless coup on September 19 by saying that widespread corruption during Thaksin's five years in office had undermined democracy.

He quickly revived the nation's dormant corruption watchdogs and set up his own high-powered team of investigators to look into allegations of graft by Thaksin and members of his government.

Sonthi acknowledged that the military could lose the public support it has generally enjoyed so far if nothing emerges to back up the corruption claims.

"We have tried to abide by the law and take all parties' concerns into account," he told the Nation.

"For example, the international community is watching to see whether human rights and civil liberties are being violated" during the corruption probes, he said.

"I know how the people feel. I guess I feel the same way when I watch soccer. I am always frustrated when waiting for my team to score and feel like getting on the field and playing myself," he told the paper.

Sonthi said the military was still on guard for a possible counter-coup movement, and warned Thaksin not to try to return home yet.

"If he's really concerned about the country, he shouldn't try to come back at present," Sonthi told the Nation.

"For people who used to have so much and lose it so swiftly, it's hard to come to terms with that, and they may do everything necessary to get it all back," he said.

Thaksin was in New York when the coup happened, and has stayed in exile in London since then.