Close to the MRT (about 3-4 minutes) and about 10 min total with train to the city centre. Ark himself is very friendly and have good instructions. For example me and my boyfriend came late at night and he gave the best introductions to go from the airport to Arks Hostel and how to "check ourself in".
Ark helped with how to go to the city centre and what there's to do in Singapore. I would definitely go back to stay at Arks and I'm surely going to recommend Arks to friends and family who's going to Singapore and want to live on a tight budget.