The Scottish Premiership club have an option to extend the 29-year-old's deal by a further year.
Emmanuel-Thomas last played for PTT Rayong, who folded after finishing 11th in the 2019 Thailand top flight.
"He's a number of years left playing top-level football," head of football operations David Martindale said.
"He has shown a tremendous desire to get back playing at the top level and we are very excited at what Jay can bring to the table."
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