Avid traveller and frequent flyer Charles David shares his memorable highlights from all his trips around ASEAN, and what every traveller-to-be should know — from a backpacker’s point of view.1. VietnamHighlight: The most memorable event was the Cu Ci Tunnel exploration for me. It awed me because it looked so plain and deserted from the top, but there was a much larger network of tunnels that underlie much of the country.