Aberavon soon replied though, a superb run from deep by winger Stef Andrews setting up an attack with full back John Phillips in support. He then found Jamie Davies who spotted the gap and raced through to score in the corner though the fly half was unable to convert.
Thomas then missed a second effort at goal, a wasted opportunity given that the Wizards then added their second try. This time around it was Phillips who was the scorer, Davies converting for a 12-3 lead.
And although Swansea saw hooker Scott Otten yellow carded for killing the ball, the score remained the same up until the half time whistle.
As the second half got underway, Aberavon's hopes of making the most of their man advantage went up in smoke as the numbers were soon levelled - Aberavon centre Mathew Jenkins sent to the sin-bin for a late tackle.
However, it was the Wizards who continued to look the better side and a chip through by Davies was almost pounced on by Andrews, only for the Whites' defence to scramble back and save a certain try.
Two more Davies penalties gave Aberavon some more breathing room and although Swansea's replacements were making an impact, a try was not forthcoming. And with flanker Matthew Davies yellow carded too, it left the Whites struggling to get back into the game.
And although Richard Williams scored in the corner with 80 minutes up, it was Aberavon who progressed to a tie with Bridgend this weekend.