The Toulouse full-back risked his injured right knee to help the reigning European Cup champions defeat the Scarlets 49-42 on Saturday.
Thomas appeared to struggle in the final moments of the 11-try feast, but the 31-year-old, who had his leg heavily bandaged at Stradey Park, reassuringly said he will be ready for the Twickenham match on February 4.
"I'll be going to the England game full of confidence and full of running," he said.
"It wasn't ideal for me on Saturday and it was difficult for me to run because my leg was so heavily strapped but I'm looking forward to next weekend's game against Pau and then, if selected, the England game.
"I had a bit of a problem in the last five minutes but once I started jogging it was fine.
"I'll have a good week training with Wales, they've got some new device for my knee, it's something for horses, I hope it's for racehorses and not carthorses, and I'll have loads of physio.
"It was important for me to play, coming back to Wales and it was a massive game for us [Toulouse]. I had to play a match before the England game.
'I feel great, but I'll feel even better come Monday when I am back in the squad with the boys. It will take more than this knee to stop me playing."
Thomas played his part in the thrilling encounter in Llanelli and would have had his name on the scoresheet had he not embarrassingly dropped a try-scoring pass in the opening minutes.
"That was bad," Wales' leading try-scorer said afterwards. "Hopefully there won't be too many of those again, but these things happen."
Thomas was full of praise for a Llanelli side that battled from 49-30 behind to come within a converted try of the French aristocrats.
"We have played some top teams in Europe and in the French league and no team has pushed us as close as the Scarlets have," he said.
"It was a great game of rugby and a great advertisement for French and Welsh rugby. If we hadn't brought our strongest team we wouldn't have won. It was important to get a home quarter-final tie because it's an intimidating place for any team to come."