Thai authorities have convicted two bar workers for the murders of the British backpackers, amid allegations that the suspects made confessions under duress.
Mr Miller and Miss Witheridge were brutally murdered on the holiday island of Koh Tao in September.
Zaw Lin and Wai Phyo have been sentenced to death.
The activitist group Anonymous has joined the protest against the convictions of two Burmese men for the murder of David Miller.
Zaw Lin and Wai Phyo, also known as Win Zaw Htun were sentenced to death in Thailand on Christmas Eve for murdering Jerseyman Mr Miller, 24, and fellow British backpacker Hannah Witheridge, 23.
The group Anonymous has posted a public message to the parents of David and Hannah.
You can read the message in full here.
David Miller from Jersey, and Hannah Witheridge from Norfolk were found dead on a beach in Thailand in September 2014.
The Miller have told ITV News they are against the death penalty issued to the two men convicted of David's murder. The pair are appealing.
A human rights activist defending the men found guilty of murdering David Miller says the 'botched' investigation can't prove their guilt.