The status of the health of 74-year-old Thaksin was not immediately clear.
Corrections department officials had on Tuesday said Thaksin had pre-existing issues with his heart, lungs and spine and blood pressure, and he would be monitored closely.
"The prison has assessed the situation and saw that it lacks doctors and medical equipment that can take care of the patient so he was sent to the police hospital," Assistant National Police Chief Lieutenant General Prachuab Wongsuk told Reuters.
Prachuab did not specify the health problem.
The Supreme Court confirmed on Tuesday Thaksin would have to serve eight years in prison after convictions for abuse of power and conflicts of interest.
(Reporting by Panarat Thepgumpanat; Writing by Martin Petty; Editing by Michael Perry)

Former Thai prime minister Thaksin Shinawatra arrives at Don Mueang airport in Bangkok, Thailand, 22 August 2023. Shinawatra returned to Thailand after living in self-imposed exile for 15 years, following his overthrowing by a military coup on 19 September 2006. The former prime minister is expected to face imprisonment with a combined jail term of five years. EPA-EFE/RUNGROJ YONGRIT