"Here's who we have booked for the #VeronicaMars series, so far. (More are on the way, I swear.)," Thomas said on Twitter Monday alongside photos of the actors as their characters.
Bell recently confirmed that "Veronica Mars" would be returning with a fourth season on Hulu.
The streaming service will also offer the program's three previous seasons next summer.
"Veronica Mars," which followed a teenage private investigator, aired for two seasons on UPN in 2004 before a third and final season aired on The CW.
Thomas then directed a 2014 feature film that was funded through Kickstarter.
The series -- which also spawned two books co-written by Thomas and Jennifer Graham -- also starred Teddy Dunn, Tina Majorino, Chris Lowell and Ryan Hansen who all returned for the film.
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"Spring breakers are getting murdered in Neptune, thereby decimating the seaside town's lifeblood tourist industry," Hulu said about the upcoming season.
"After Mars Investigations is hired by the parents of one of the victims to find their son's killer, Veronica is drawn into an epic eight-episode mystery that pits the enclave's wealthy elites, who would rather put an end to the month-long bacchanalia, against a working class that relies on the cash influx that comes with being the West Coast's answer to Daytona Beach."
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