MAE SAI (THAILAND) - I am standing in the grounds of a Buddhist temple, at the entrance to a dark cave, when I hear a male voice from behind me. "They say that cave goes all the way from Thailand to Myanmar."

I turn around to be greeted by a Swiss monk who is living here at Wat Tham Pha Chom, an ancient Thai temple located just 200m from the Ruak River, which forms a natural border between Myanmar and Thailand's Chiang Rai Province.