The 38-year-old former Manchester United midfielder and current Wrexham captain left hospital yesterday after treatment for stab wounds suffered in the assault on Thursday night.
Last night North Wales police said a 29-year-old woman arrested in connection with the attack had been released without charge. Two men were still being sought.
The attack happened at about 10.15pm, when Thomas parked his Volkswagen in a country lane at Dyserth, near Prestatyn, Clwyd, and the window was smashed, a police spokesman said.
A motorist took him to Glan Clwyd Hospital at St Asaph. Doctors said the player suffered a suspected fractured jaw or cheekbone, other facial injuries, and 15 stab wounds to his left buttock, back and left leg. Police said they were still investigating the motive.
Thomas is awaiting trial on charges of handling forged banknotes.
One of the oldest professional players, he won 51 caps for his country, and has played for 10 league clubs during a turbulent career. At Manchester United, he failed to turn up for a summer tour of Malaysia in 1981. At Brighton, he went missing several times and was fined and suspended.
He was transferred to Stoke City, nearer his North Wales home, where he had the first of several marital break-ups. Thomas eventually returned to Wrexham and helped them to a surprising win over Arsenal in the FA Cup last season.Reuse content