They never recovered from the opening-day defeat by Italy as encouraging performances against England and Ireland were tempered by sub-standard displays against Scotland and France.
Wales have been a model of inconsistency this season, an ominous sign given that they are due to tour Australia and New Zealand in the summer before competing in the World Cup in little over six months from now.
But while Thomas believes a change in Welsh fortunes may come too late for the World Cup, he feels there is enough talent in the side to suggest they could blossom into something special.
"We have definitely made progress this season. It's been a tough 6 Nations for the boys and there's been a lot of criticism, but that's just brought us closer together," said the powerful Bridgend back.
"In a year or two the team we have now will be a fantastic side. We just have to work away at securing a victory - that's all this team needs.
"There is fantastic talent in the squad - the likes of Rhys Williams, Craig Morgan, Tom Shanklin and Martyn Williams are, in my book, world-class players."