The Jim Bolger-bred and trained Theobald is now guaranteed a free start in the £150,000 Sun Racing All-Weather Mile Championship on the same surface at Lingfield Park on £1-million All-Weather Championships Finals Day, Good Friday, April 19.
Theobald, ridden by Kevin Manning, was always prominent, racing in second behind the leader Geological (Damian English/Rory Cleary, 8/1) before going ahead with a furlong and a half remaining.
The four-year-old Teofilo colt ran on to beat All-Weather Mile stalwart Captain Joy, now 10, by a length and quarter in 1m 37.12s, with Tony The Gent (Ger Lyons/Sean Bird (10), 7/1) a short-head back in third of the seven runners.
Ger Flynn, Bolger's travelling head lad, reported: "The option to go to Lingfield for the Final is there if the boss wants.
"Theobald is progressing, loves Polytrack and hopefully it is onwards and upwards with him."
Theobald, twice runner-up in G3 races as a two-year-old, has now won on three of his five starts at Dundalk, as well as gaining a third.
10-time All-Weather scorer Captain Joy (Tracey Collins/Wayne Lordan, 11/2), whose owner Herb Stanley died on January 3 at the age of 81, returned to form, coming to challenge inside the final furlong before finding no extra.
Dundalk's eight-race programme saw trainer Adrian McGuinness enjoy a 92/1 treble with All's Quiet (Rory Cleary, 7/1), Georgian Bay (Tom Madden, 4/6) and Ken's Sam's (Shane Foley, 6/1).
Picture All-Weather Championships