Bai Tu Long bay to Hoi An is very popular router for travellers coming to Vietnam. To do this, there are 2 ways as following:
From Bai Tu Long bay, Quang Ninh, you can take taxi to # 64 Quang Trung st. – Uong Bi city to catch night bus at 19h or 22h24. It takes 19 hours 40 minutes drive to go!
Or take bus/private car to 05 Pham Ngu Lao – Luong Khanh Thien – Ngo Quyen – Hai Phong, to catch bus at 9h, 18h30, 19h, 19h30. It takes 17 hours 20 minutes drive to go!
From Bai Tu Long bay, take bus or private car to get to Cat Bi international airport, flight to Danang and catch taxi or bus to Hoian. This is the most common way to save time!