Indian Railways operates a train from Asansol to Mandarmani once a week. Tickets cost $6 - $19 and the journey takes 6 h 31 min. Alternatively, you can take a bus from Asansol to Mandarmani via Kolkata(Easplanade), Kolkata, and Digha in around 9 h 54 min.
From Asansol Junction (ASN) train to Kanthi P H (KATI) then taxi to Mandarmani. 6 h 55 min ₹1,531. From Asansol bus to Kolkata(Easplanade), walk to Kolkata, bus to Digha, then taxi to Mandarmani. 9 h 54 min ₹1,939. From Asansol taxi to Mandarmani. 4 h 22 min ₹5,863. From Asansol drive to Mandarmani. 4 h 22 min ₹2,352.