On Sunday Sonthi accepted a mandatory retirement from the army and announced his resignation the following day as head of the Council for National Security comprising other coup leaders.
The council shares power with Thailand's interim civilian government led by Surayud Chulanont, the incumbent prime minister.
Sonthi led the bloodless coup that overthrew the government of Thaksin Shinawatra and installed Surayud as prime minister.
The coup leaders have pledged to restore democracy before the end of the year and elections have been scheduled for December 23.
Sonthi's appointment, which took effect on October 1, was endorsed by King Bhumibol Adulyadej as "appropriate and beneficial to the government's work".
|Surayud, left, said Sonthi wouldl help |
him with security issues [Reuters]
Denying allegations of harbouring political ambitions, Sonthi said he was only helping to oversee the country's security, stating that a crack down on drug traffickers will be his first priority.
"Taking up this post at this time should not be seen as me trying to cling to power," he said. "I am accepting this burden to help the government oversee our country. I am not getting into politics."
The September coup was the culmination of a months of political unrest amid allegations of corruption involving Thaksin, the then-prime minister, and his family.
Recently Surayud's cabinet has been rocked by a growing shares scandal which forced five ministers, including the interior minister, and a top government spokesman to resign.
The five ministers and the spokesman stepped down after being accused of breaching shareholding limits imposed by anti-graft laws.