A Czech man is facing up to 12 years in jail on charges of knowingly infecting nearly two dozen people with HIV, prosecutors said Wednesday, after flying him home from Thailand where he was arrested.

Zdenek Pfeifer, 49, was questioned after more than a year on the run over eight offences including spreading a contagious disease, said Vladimir Jan, a spokesman for the prosecutor's office.

Czech police say he knew since 2013 that he had HIV but had sex with at least 23 men across the Czech Republic without informing them, infecting at least three including a 13-year-old boy.

Officers believe the number of victims could actually be substantially higher. It was not immediately clear whether he would also face statutory rape charges.

After being flown from Thailand guarded by five Czech police officers, Pfeifer was put in provisional detention in the northwestern town of Usti nad Labem.

"The accused could face five to 12 years in prison," Jan said, quoted by the CTK news agency.

"The start date for his trial has not been set yet," Usti nad Laben regional court spokeswoman Marcela Trejbalova said.

Pfeifer first entered Thailand in June 2015 on a tourist visa which ran out two months later.

He was detained at his apartment on the resort island of Phuket earlier this month after reports warning of his presence in the popular holiday nation went viral on Thai social media.

Nathathorn Prousoontorn of Thailand's immigration police told reporters that no complaints had been filed in the Asian nation alleging that Pfeifer had knowingly infected anyone there.