There was heavy police security outside his residence.
Pheu Thai Party leader Paetongtarn Shinawatra's Benz van departed from the family mansion at around 4.40am and arrived at Police General Hospital at around 5am.
Thaksin returned to his residence in the van at 6.30am, accompanied by high-level police after a 30-minute ride. Inside the car were Thaksin, sitting on the left, Paetongtarn on the right, and another daughter Pinthongta Shinawatra Kunakornwong seated at the back.
Observers said Thaksin looked composed, wearing a soft splint cervical collar around his neck, likely due to his recent health issues related to a spinal condition and nervous system. He has been under the care of specialised orthopaedic physicians at the hospital.
Thaksin was wearing a combination of green and navy blue colours, which some experts said were considered auspicious for Sunday.
Thaksin, 74, are among 930 convicts to be released on parole this month, in a Department of Corrections directive approved by Justice Minister Tawee Sodsong.
The ex-PM is entitled to parole after having served at least one-third of his prison term or six months, whichever is longer, according to the Corrections Department regulations on granting parole for inmates who are 70 and over or seriously ill.
Thaksin was sentenced in absentia to eight years in prison for corruption stemming from his 2001-2006 tenure as prime minister, which was cut short by a military coup. However, he received a royal pardon soon after his return to Thailand last year, which reduced the sentence to one year in jail.
The former premier flew back to Thailand on a private jet on August 22, ending 16 years of self-imposed exile overseas. Less than 24 hours after landing on Thai soil, he was sent from Bangkok Remand Prison to the Police General Hospital for treatment of unidentified health issues. He has reportedly been there ever since.
His long hospital stay aroused suspicions about the seriousness of his illness while leading to allegations that he was enjoying VIP treatment from the authorities. Some even suspected that Thaksin was no longer at the hospital.