Yingluck's lawyer says she was too ill to attend, but a senior member of her party has suggested that she's fled to Singapore.
"I never questioned her about this, and I don't want to intrude on my client", he said. The doors of her home were shut and local media said there had been no movement there since the early morning.
Thitinan said Yingluck's decision to skip the verdict hearing will have "emboldened" the military government.
An official of Yingluck's Pheu Thai party who is close to the Shinawatra family told The Associated Press she was no longer in Thailand. The ruling junta would have fewer obstacles to maintaining its grip.
Historically the Shinawatras have been able to mobilise huge crowds of supporters - known as the "red-shirt movement" - to take to the streets when the family's political fortunes have waned.
Depressing cycles of elections, protests, coups and military regimes dominate Thai politics.
She has pleaded not guilty to the charges, saying she is the victim of a "subtle political game".
Yingluck came to power in 2011 and soon after delved into the controversial rice subsidy program, which wreaked havoc on the country's rice market.
The case centers on whether Ms. Yingluck mismanaged a subsidy program that led to a stockpile of rotting rice, but it carried significance far beyond inflated grain prices. Vietnam as a result replaced Thailand as the world's leading rice exporter.
"The military government have been suppressing dissent and suppressing demonstrations".
Yingluck already has been held responsible for about $1 billion of the losses in an administrative ruling that froze her bank accounts.
Before Yingluck's trial kicked off, some had speculated whether she would follow her brother's footsteps and leave the country. Acquitting her, though, would have been equally unacceptable to her hard-line opponents, many of them very influential.
"The court ruled that "...it was not convincing that the defendant was sick to the extent of being unable to travel to the court". It remains to be seen who will replace her as party leader, and what will happen when the military's ban on political activities is lifted ahead of a general election - which is not expected to be before the fourth quarter of 2018.
The court cases and possible criminal conviction aside, Yingluck retains great popularity with her base. There was money to buy luxuries and to invest in their farms.
In a Facebook post on Thursday, Yingluck asked her followers to stay home for the trial because she was anxious that people with "ill-intentions" might cause trouble. "We are looking for her".
Thaksin left Thailand in 2008 just before the Supreme Court sentenced him to two years in prison for conflict of interest, in which his then wife bought state land in Ratchadaphisek area of Bangkok during his tenure as prime minister.
Yingluck denies the negligence charges.
It has fuelled speculation she has joined her brother, fellow former premier and ex-Manchester City owner Thaksin Shinawatra, in self-exile.
Some analysts agree, and believe the prosecution's approach sets a unsafe precedent.