This victory qualified him to play in the Asian Junior Chess Championship 1983, which took place in Kuala Lumpur, Malaysia. Gunawan played for Indonesia in the Chess Olympiads of 2000 in Istanbul, and 2004 in Calvià. He died at the age of 38 in Manado because of heart failure and pneumonia that he had during the Calvià Olympiad.
Born in Jakarta, his earlier achievement was winning the Indonesian U16 championship in 1982 in Bandung. Ruben Gunawan won the championship and was awarded the FIDE Master title. In 1984 he won the Indonesian U19 championship. He achieved the 1009th rank at FIDE position on July 2005. His Elo rating at that time was 2463, while the highest rating he ever achieved was 2507 in January 1999.
