JJ Williams feels Gareth Thomas will not play for Wales again after he was banned for a month, ruling him out of the first three Six Nations games.
Thomas is Wales' all-time leading try-scorer
"He lets himself down and I doubt if we will see Gareth Thomas come back," said ex-Wales and Lions wing Williams.
"I think it is very unlikely that we will see him play for Wales again."
Thomas flicked his middle finger at Ulster fans in a Heineken Cup game and was also found guilty of aggressively attempting to jump into the crowd.
"You just can't do that," said Williams. "From the history of time you are going to get stick from people in the stand. That is part and parcel of it all.
"You can't react like that, and it is not the first time.
"Gareth was in trouble with Bridgend down in Pau and then the BBC interview last year on Scrum V [about his role in the departure of head coach Mike Ruddock]."
Welsh Rugby Union group chief executive Roger Lewis says that the Union do not condone inappropriate behaviour by any player at any level within the game.
The WRU is considering the implications of the Thomas ruling and considering whether to appeal against the ban.
Ex-Wales and Lions captain Thomas, who will join Cardiff Blues from Toulouse next season, has already announced his plans to retire from Test rugby after the World Cup.
The 32-year-old utility back is Wales' all-time leading try scorer with 37 from his 90 caps.