The men have been charged with the murder of both Britons -- a charge which carries the death penalty -- and the rape of Witheridge, with police saying that their DNA matched samples taken from her body.
"The two Myanmar nationals are charged with murder (of both tourists), gang rape (of Witheridge) and stealing," Prachum Ruangthong, police chief of neighbouring Koh Phangan island, told AFP.
The breakthrough follows intense scrutiny of Thai authorities, which had been accused -- in criticism led by the British media -- of bungling the investigation in the days after the crime.