The victim called police at about 7am on Sunday, November 6 to report being set alight while sleeping in the Royal Arcade, police said.
The 51-year-old, who sustained minor injuries to his head, cheek and eye lids, also had his rucksack stolen, police confirmed.
Officers said they would like to speak to the three people pictured as part of the ongoing investigation.
Anyone who recognises them is asked to report it online at https://sussex.police.uk/contact-us/response-to-appeal/ or call 101, quoting serial 273 of 06/11.
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