Thomas' first-innings haul of 6-60 was his best figures in English first-class cricket
Alfonso Thomas took three more wickets to finish with match figures of 10-88 as Somerset beat Sussex inside three days to strengthen their title hopes.
Sussex resumed with a lead of 53 on 94-4, but they soon slumped to 94-6 as Thomas struck twice in three balls to remove Michael Yardy and Ben Brown.
Thomas finished with 4-28 and Murali Kartik 4-46 as Sussex were dismissed for 134, setting Somerset 93 to win.
Marcus Trescothick then hit 54 not out to guide his side home by nine wickets.
Somerset collected 21 points for their victory to increase the pressure on fellow challengers Durham, Lancashire and Warwickshire at the top of the table.
Morning rain prevented any play until after lunch, and overnight batsmen Yardy and James Anyon played out four maidens before Thomas struck a double blow by having Yardy caught at third slip by Kartik before pinning Brown lbw two balls later.
There was little further resistance from Sussex as Charl Willoughby had Ollie Rayner caught behind, before Kartik trapped both Anyon and Monty Panesar leg before.
Thomas then wrapped up the Sussex innings by having Wayne Parnell caught in the slips by Trescothick at the second attempt to claim only his second 10-wicket match haul.
Sussex coach Mark Robinson told BBC Sussex:
"We turned up and we knew it was a three-day result wicket. It turned from ball one.
"To get them to 93-7 was dreamland, but it started to go pear-shaped from there.
"We lost two wickets late last night and two early today so we were always struggling.
"We probably showed a lack of aggression when batting but in the game you end up playing to the situation."
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