For me
Several caves. Big one in Phattalung, cave in Trang on a boat that has a low ceiling, Tham Lot in Soppong.
Boat trips - Emerald cave, Ko Hong, other islands.
Nightclubbing in Bangkok.
Riding bikes around islands. Driving up north.
Kayaking trips thru mangroves.
Longtail boat in Kanchanaburi.
Patting a tiger. Riding an elephant thru jungle.
River rafting.