The teams are starting from the third checkpoint in Phnom Penh, Cambodia. It's the end of the Cambodian national holiday, Pchum Ben — meaning Ancestors' Day — and the teams have a chance to receive a blessing and pay respects to loved ones. Then the remaining pairs must leave the checkpoint and travel 1,400 kilometres through Thailand, one of the most visited countries in the world, to the Shan Highland that straddle the Thai-Myanmar border, where the fourth checkpoint is situated in the sleepy mountain town of Mae Sariang. To reach the checkpoint, the teams must first circumnavigate the Tonle Sap Lake and decide whether to head west, taking on potentially faster routes, or opt for the eastern route, where lies Siem Reap, the gateway to Angkor Wat. But from there it's a journey back in time through Thailand's rural eastern provinces, and a longer and circuitous route rarely travelled by backpackers.