I cannot say whether you are right or wrong here, but I cannot imagine countries jailing former PM's for things they did while still in office.
Look at Blair in the UK, if any PM deserved to be jailed it is him, does WMD and Iraq not spring to mind?
I cannot believe that Yingluck has done worse than that, and don't forget the soldier who led an illegal coup and stayed in office here for nine years, protected only by soldiers, guns and tanks.
Neither Yingluck or her brother have done worse than that either.