Wales started their championship with a convincing 25-8 victory over Italy before being beaten 40-12 by Ireland in round two.
Next up for the team led by head coach Ioan Cunningham is a meeting with France – a team which have been powerhouses at Under-20 level for the last three seasons.
“It was hugely disappointing coming off the performance and result against Italy,” Thomas said of the reversal to Ireland.
“That was a huge high for the boys. Some of them hadn’t played for 18 months and it was as if it was their World Cup final.
“They probably fell off the edge of the cliff after the game and to get emotionally up for Ireland was a huge learning curve about staying on an even keel.
“We were still riding the emotional wave from Italy. As staff we could have tried to bring them down a little bit and then got caught out by the better team on the day.
“We’ve tried to worry about ourselves with a six-day turnaround.
“We are an inexperienced squad with a lot of first years. Look at the little things Ireland did off the ball – they were a lot more streetwise.
“A year at this age is huge, but our younger boys learnt so much from that game. It was a huge learning tool for their development.”
Wales face France on Thursday and targeting improvements for that game, Thomas added: “From a line-out point of view we haven’t been happy with how we have started each game.
“It’s been a little bit inconsistent. We’ve put a huge emphasis on our start, the basics, and making the right calls in the right areas of the field.
“Some of the players hadn’t played for nearly two years and we’ve got some boys who are still in school who haven’t even been away from home.
“The start of the game was huge for us. Our possession and territory hasn’t been great in the last two games.
“Our scrum was really good last week, but our line-out didn’t help us achieve what we wanted to.
“We’ve got to get our roles right because we caused Ireland some problems when we did that.”
