The defence team for Zaw Lin and Wai Phyo, the Myanmar migrant workers accused of the September murders, earlier petitioned the court to have the DNA evidence re-examined.
The judge heard the argument that it was necessary to prevent a "miscarriage of justice," officials at the Samui Provincial Court said.
The badly beaten bodies of David Miller, 24, and Hannah Witheridge, 23, were found on Sept 15 on Sai Ree beach in Koh Tao. Zaw Lin and Wai Phyo were arrested in October and confessed to the crimes, but later withdrew their statements saying they were tortured.
British and Myanmar envoys have raised concerns about the Thai investigation, with London sending a police team as observers.
The National Human Rights Commission of Thailand also expressed concern about the alleged forced confessions. Thai police have denied the accusations of torture or misconduct.