Several Thai media outlets have run photos of former Prime Minister Yingluck Shinawatra and her fugitive brother and former prime minister, Thaksin Shinawatra, taken at a major tourist spot in Washington DC, the US capital.
The media reported Wednesday that the duo was going to stay in the United States for some time before returning to Europe in June.
The photos show the Shinawatras posing together at the Lincoln Memorial, though it is unclear when they were taken.
Deputy police chief Srivara Ransibrahmanakul said police were trying to determine when the picture was taken.
The duo has recently been seen visiting other countries together, including Japan, China and Singapore.
Yingluck, who was prime minister from 2011 until she was ousted by Thailand's Constitutional Court shortly before a May 2014 coup, fled the country last August amid a criminal court case against her.
The following month, the Supreme Court sentenced the former prime minister in absentia to five years in prison for mishandling a rice subsidy project that caused massive losses.
The BBC's Thai-language website reported this week that Yingluck had obtained a multiple-entry visa from Britain that allows her to be in the country over the next 10 years as long as each stay is six months long or shorter.
Thaksin, a former telecommunications mogul who served as prime minister from 2001 to 2006, has been living in self-imposed exile since 2008, having been stripped of much of his wealth by subsequent Thai governments that charged him with corruption and conflicts of interest.
