The 23-year-old Welshman, who won the British Grand Prix on Sunday in 44.49, finished second behind the world record holder, Butch Reynolds, who recorded 44.08, with another Briton, Mark Richardson, finishing strongly in fourth place in 44.70.
Reynolds, who failed to finish in the first three at last month's US trials, will not be running in the World Championships. But Thomas's rising hopes were checked yesterday by strong rumours that the International Amateur Athletic Federation is to offer Michael Johnson, among others, a wild card for Athens.
Although the Olympic 200 and 400m champion missed the US trials with injury, an IAAF source indicated yesterday that the federation was preparing to offer defending champions of 1995 the right to contest their titles.
"I think you will find that there is a majority of people in the IAAF who are in favour of this and it will be in place by Athens," the source said.
"Not all athletes and officials like the idea, but it is seen as a way of making the World Championships different from the Olympic Games. It helps top athletes who are injured and missed national trials to make the event. It basically improves the championships as a show."
However, the IAAF general secretary, Istvan Gyulai, said no decision had been made.
Thomas, who held on well after adopting his usual tactic of a fast start, was against the idea of awarding Johnson a run in Athens. "If you give a wild card to him you have to give it to everyone. It's a bit unfair," he said. "But I'm not scared of anyone."
With Johnson still clearly far from peak form following his injury in the Toronto 150m challenge against Donovan Bailey, Thomas and Richardson look like contenders whatever the field.
Only one Briton has run faster than Thomas - Roger Black, the British record holder at 44.37, who pulled out of last night's meeting with what has been confirmed as a virus.
Further blood tests will reveal whether the 31-year-old double Olympic silver medallist is suffering from a repeat of the Epstein Barr virus which ruined his 1993 season.
Bailey lost out over 100m last night, finishing third behind the 22-year- old US champion Maurice Greene, who was timed at 9.90. Linford Christie finished seventh in 10.12. Frankie Fredericks, the double Olympic silver medallist last year, was second, 0.01sec behind Greene.Reuse content