Grab banana pancakes, mango sticky rice or jok from a popular Khao San vendor to ease into Thai street-food culture; great introduction to local flavours.
Take the morning train from Bangkok Hua Lamphong to Ayutthaya (approx 1.5–2h) for a full-day temple bike tour; trains run frequently from early morning.
Early-morning alms-giving is a moving cultural experience — be respectful: observe from a distance and follow local guidance (best to watch rather than participate unless informed).
Visit the sacred springs at Tirta Empul (ritual purification) and the nearby Gunung Kawi rock-cut shrines; best in morning to mid-afternoon (open 7:30am–5:00pm).
Visit Lempuyang Temple (famous gates), Tirta Gangga water palace and seaside villages — start early to avoid crowds at Lempuyang (temple is open early morning).
Book a diving/snorkelling trip (Nusa Lembongan or Padang Bai) for colourful reefs and marine life — most boats depart morning and return late afternoon.