Williams was a key figure in helping the newly-named Bears secure promotion back to the Aviva Premiership from the Championship last term before making his move to the Dragons.
The 24-year-old is looking forward to the PRO 14 campaign but has taken time out to thank Bears boss Lam and feels the former Samoa international had a big influence on his career.
He told Dragons media: "Last year was a good year for me learning a lot off Pat Lam.
"I've grown up a lot and moving over to Bristol helped that. Going to Bristol was a fresh start and out the goldfish bowl as some say.
"It was an opportunity to start enjoying my rugby again and I'm glad I made that decision."