Join a short guided trek through the Mossy Forest and highland trails for unique flora and cool-air hiking (guides/bookings recommended; tours start morning).
If you didn’t take the night train, you can use the morning to visit the Fine Arts Museum (opens 8:00am) or relax before travel; otherwise sleep in after sleeper transfer.
Breakfast on board and light morning excursion before returning to the Halong pier around mid-morning (cruise returns ~9:00–11:30 depending on operator).
Rent a bike or join a low-cost morning cycling tour around Tegalalang rice terraces to see terraces and local life; many tours start early to avoid heat and crowds (Tegalalang open all day).