Renault dismissed suggestions that meant it was lining him up to replace Jolyon Palmer later this season, instead saying Kubica's participation in the test was to assess his chances of making a comeback in 2018.
Hamilton said he wanted to see Kubica return to racing in F1.
"I'm really happy that he's doing the test, and I'll have a keen eye on how he's doing," said Hamilton, who wants to follow "how his tests are going" and "whether or not he's going to be racing".
I think it will be great if he's able to [return], if he can, physically. [He has] raw, natural talent, which I think as a sport it's a shame we don't have here with us.
Robert Kubica (Lotus) - Test - Cheste 06/06/17
Image credit: Renault Sport
Kubica's best F1 season came in 2008, when he finished fourth in the championship while driving for BMW Sauber and led the points after winning the Canadian Grand Prix.
Hamilton, who went on to win that year's title, said Kubica would have been a regular championship contender had his career not been disrupted.
"Robert's one of the quickest drivers I've ever raced against," he added.
"If he was still racing today he'd been in contention for a world title, if he'd [already] not won one.
Not a lot of great, great drivers come through. You have some that are much better than the rest, but still not the greatest, and then you have real special drivers like him.