Former prime minister Thaksin Shinawatra is set to arrive at Don Mueang airport on Aug 10, his daughter Paetongtarn "Ung Ing" Shinawatra announced on Instagram on Wednesday.

"I can't quite believe what I am typing, my father is returning on Aug 10 at Don Mueang airport," Ms Paetongtarn wrote on her father's 74th birthday.

According to the Pheu Thai Party's prime ministerial candidate, she had missed only three of her father's birthdays, with the latest one being this year.

"(Our family) is both glad and worried, but we always respect our father's decisions," Ms Paetongtarn wrote.

Ms Paetongtarn also wrote that her father was a prime minister who was recognised for having the most national contributions, but he also faced hardships and mistreatment.

Thaksin had mentioned his plan to return to Thailand since early last year, she wrote.

Since being overthrown by a military coup on Sept 19, 2006, Thaksin has been living in self-imposed exile, except for a brief visit to the country in 2008. During his absence, the Supreme Court sentenced him to a total of 12 years in prison in four corruption cases.