The Bangkok Post reports Shinawatra said Thai citizens would not accept the current military government for long and would soon join him in his call for a return to democracy.
"We have tasted democracy, and we believe in democracy. So it's time for Thailand to restore democracy as soon as possible," Shinawatra said.
"Democracy is in the blood of the Thais," he added. "They can tolerate (a non-elected government) for a period of time -- one year, one year and half -- but then the return of democracy is necessary."
The former prime minister alleged the current state of the government is damaging Thailand's standing in the international community.
Thailand's military leaders have pledged a return to democratic rule by the end of 2007 through the beginning of elections, the Bangkok Post said.