Jones missed the opening two wins of the tournament due to a calf muscle injury - with the former captain having last played in the warm-up loss to England at Twickenham.
However the 30-year-old has returned full training, with Jones taking part in a public session at Waitomo Rugby Club on Thursday.
"It looks as if Ryan has come through the session well," Wales assistant coach Rob Howley said.
"At this moment in time, he is fully fit and available for selection. Ryan was smiling and happy, which is always a good indicator.
"It looks as if he is up and running."
The return of Jones will be a welcome boost for Wales after full-back James Hook (shoulder) and flanker Dan Lydiate (ankle) were injured in the win over Samoa.
Wales coach Warren Gatland will name his team on Saturday, with several changes expected, including likely starts for Stephen Jones, Gethin Jenkins, Lloyd Burns, Craig Mitchell, Scott Williams and Lee Byrne.
Howley added: "When you look at the side that will start against Namibia, it will be a far more experienced side than that which took the field against South Africa and Samoa."
Wales forwards specialist Robin McBryde, meanwhile, has underlined the importance of the team blasting out of its blocks against Namibia.
"We've got to go out as hard as we can," McBryde said.
"Samoa and Fiji showed the way (against Namibia). They just went out hard from the word go and got the result first, then concentrated on the performance afterwards.
"I think that is the way we've got to go as well. The outcome of the group is undecided. I think it's going to go all the way, and who knows what is going to happen in the other fixtures?
"Samoa and Fiji have got a lot to play for, and I don't think South Africa will take Samoa lightly."
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