By Agence France-Presse
Yingluck, whose government was toppled by the military in 2014, staged a disappearing act before a scheduled court judgement last Friday in a criminal negligence trial.
She faced up to ten years in prison and a lifetime ban from politics if convicted. But instead she was a no-show, with junta and party sources saying she had fled abroad.
Thailand's junta has come under fire from some conservative allies over Yingluck's disappearance, with many questioning how the authoritarian regime could have let her flee given that she was heavily monitored.
Army chief General Chalermchai Sitthisad gave a lengthy defence on Tuesday, which offered insights into how military intelligence kept track of Yingluck and how she might have slipped the net.
"As of now we learnt that she abandoned all of her phones and changed her cars so it was hard to trace her using the same methods we did before," he told reporters, confirming military intelligence had previously used electronic and physical surveillance.
But Chalermchai said officers had recently been withdrawn from guarding the front of her Bangkok house.
"The public alleged that it was violating her personal rights and intimidating her so we withdrew the force," he said.
Yingluck frequently complained of being constantly followed by military intelligence since she was ousted from office.
Thai media has been full of speculation about how she might have escaped, with most suggesting she went to Cambodia either by land or sea in the days before the court verdict and then on to Singapore.
A senior junta source told AFP they believed she had fled to Dubai, the base of Shinawatra family patriarch Thaksin, a billionaire who is Yingluck's older brother.
Chalermchai said he thought it was unlikely Yingluck would have been able to fly directly out of Thailand given security procedures at airports, even for private flights. Instead, he said, a land or sea exit was more likely.
But he added that once outside Thailand she likely took a private flight organised by Thaksin.
"I believe that former prime minister Thaksin prepared a plan for her, for example a private aircraft which regular people cannot find," he said.
The Shinawatra political dynasty began under Thaksin in 2001 with a series of groundbreaking welfare schemes that won them votes and the loyalty of the rural poor.
But their popularity rattled the royalist and army-aligned elite, who assailed successive governments linked to the clan with coups, court cases and protests.
Thaksin himself was toppled in a 2006 coup and fled overseas two years later to avoid jail for a corruption conviction.
The period since then -- dubbed the "Lost Decade" -- has seen frequent deadly street protests, short-lived governments and the return of military rule in 2014.