Yingluck arrived at Bangkok's Don Mueang airport Sunday night from Singapore, the Bangkok Post reported.
Yingluck left Thailand for a holiday in Europe and the US after she was granted permission to leave the country between July 23 and Aug 10.
She was required to request permission because of pending legal allegations against her.
During her trip, she attended the 65th birthday celebrations July 26 of her brother Thaksin in Paris.
Yingluck will have to fight a high-profile case in which the National Anti-Corruption Commission (NACC) has accused her of negligence of duty in overseeing a controversial rice-pledging scheme.
The NACC has forwarded the case to the Office of the Attorney-General (OAG) for indictment.
The OAG is yet to examine the evidence and witnesses to decide if there was sufficient grounds for pressing charges against Yingluck in the Supreme Court's Criminal Division for Holders of Political Positions.
If found guilty, Yingluck could face a jail term as well as a five-year ban from politics.
In the meantime, an investigative panel of the Election Commission (EC) has alleged that Yingluck, along with eight other former cabinet ministers and national police chief, had abused power by using public funds to campaign for the already-nullified Feb 2 general election.
All involved in the case will be called to defend themselves before the panel.
The EC will have to decide whether to take the case to the Supreme Court's Election Cases Division for ruling.
If found guilty, those involved could face up to 10 years in prison, a maximum fine of 200,000 baht (about $6,186) and a 10-year ban from elections.