Haresh has been the Resident Playwright of The Necessary Stage since 1990. He was awarded the Cultural Medallion in 2015. To date, he has written more than 120 plays which have been staged in over 20 cities. His play, Off Centre, was selected by the Ministry of Education as a Literature text for GCE N- and O-Levels.

Haresh has 13 publications of his plays, including Trilogy, Shorts 1, Shorts 2, Don't Forget to Remember Me and Abuse Suxxx!!! and Other Plays. His works have been translated into Malay, Mandarin, Greek and Italian. He was awarded Best Original Script for Fundamentally Happy, Good People and Gemuk Girls at the 2007, 2008 and 2009 The Straits Times Life Theatre Awards respectively. Most recently in 2021, Haresh published Reading the Room: A Playwright’s Devising Journey, which details his devising process developed over his career at TNS. Haresh also had the honour of having a selection of his works featured at Esplanade’s first playwright-centred season at The Studios in 2017.

He has participated in several writers' festivals including the inaugural Singapore Literature Festival in New York (2014), New Delhi World Book Fair (2015), Ubud Writers and Readers Festival (2015), Hong Kong Literary Festival (2015) and Neilson Hays Bangkok Literature Festival (2019).

Haresh is the first non-American to be awarded the prestigious Goldberg Master Playwright by New York University's Tisch School of the Arts in 2011. In 2014, he was conferred the Southeast Asian Writers (or S.E.A. Write) Award (Singapore), which recognises and honours literary excellence in the ASEAN region.