David Brooks headed home a Bale cut-back from close range after 66 minutes to maintain Wales’ one-point lead over Finland – 2-1 winners in Bulgaria – before the two teams meet in their final Group B4 fixture in Cardiff on Wednesday.
It was Wales’ fourth 1-0 win in the group and leaves Ireland – who had Jeff Hendrick sent off in stoppage time for denying Tyler Roberts a goalscoring opportunity – facing a relegation decider against Bulgaria in Dublin on Wednesday.
But Ireland might feel that Wales should have been reduced to 10 men after 37 minutes when Joe Morrell lashed out at Jayson Molumby.
Both men were booked in the incident but many referees may have chosen to show Morrell the red card instead of yellow for reacting to the Irishman’s shove on him with a petulant kick.
Bale was back from injury to lead a Wales side unbeaten in nine competitive games – a sequence stretching back to June 2019 – and he had a hand in the winner 24 minutes from time.
Dan James’ cross was met by Bale at the far post, outjumping his Tottenham team-mate Matt Doherty, and Brooks bravely headed home his second Wales goal under pressure from Duffy.
Brooks and Moore were denied by Randolph in the closing stages, but Wales held on to keep a seventh successive clean sheet in competitive football to boost their Nations League promotion hopes.
Additional reporting by PA.