The decision was relayed by Mr Thaksin's legal adviser, Robert Amsterdam, and revealed exclusively by the ABC.
The announcement comes amid reports that coup leader General Prayuth Chan-ocha will remain at the head of a junta beyond his scheduled retirement in September, according to the Bangkok Post.
General Prayuth has assumed the powers to act as prime minister; except Section 2, which acknowledges that the king is the head of state.
On Saturday night the military junta disbanded the country's Senate and placed all law-making responsibility in the hands of General Prayuth.