Intermediate outfit Rathmolyon led 0-3 to 0-2 after 10 minutes.
But Michael Donnelly hit six points for Thomastown, who led by 0-8 to 0-4 at the break. With captain JJ Farrell leading by example, they increased the advantage to six points before Gary Cole blasted a Rathmolyon penalty to the net after 57 minutes.
Stung by that concession, Thomastown responded with goals from substitute Adrian Burke and Thomas O’Hanrahan.
Scorers for Thomastown: M Donnelly 0-6, 5fs, 1 65, T O’Hanrahan 1-2, JJ Farrell 0-4, 1f, D Walsh 0-1.
Scorers for Rathmolyon: G Cole 1-3 (1-0 pen, 0-2f) J Farrell 0-4 (frees).
THOMASTOWN: D Walsh; S Mahony, S Lanigan, B Murphy; B Whelan, P O’Hanrahan, R O’Hara; D Walsh, D Lanigan; D Walsh, M Donnelly, D Burke; T O’Hanrahan, JJ Farrell, D Prendergast. Subs: S Waugh for Burke (44), E Tennyson for Murphy (46), M Mahony for Prendergast (49), A Burke for D Lanigan (54).
RATHMOLYON: J Gantley; A McEnroe, G Whelan, N Cole; M Lynch, A Fagan, E Regan; N Fagan, T Cosgrave; J Fagan, T Lynch, G Cole; ; J Farrell, K Fagan, G Doherty. Subs: D Morgan for Doherty (40), T Henderson for Lynch (49).
Referee: G McGrath (Dublin).