Landing in Ho Chi Minh City - or Saigon, as the locals prefer to call it - I am met by a guide who will take me through the Mekong Delta, over the border to Cambodia and along its golden coast (with enough time for some island-hopping in the Bay of Kompong Song), then up towards Siem Reap and its ancient neighbour, the jungle city of Angkor.
Here's a top tip he gives me: most people in both Vietnam and Cambodia prefer to deal in US dollars, so no need to bring local currencies.
Before I know it, I'm back in the bus headed for the Prek Chak border crossing. It's a smooth transition into Cambodia. A conveyor belt of guards take turns stamping my passport, smiling as they wave me into their country. First stop: the seaside town of Kep.
A few miles from the border, I take a detour to Anlung Pring (mekongcrane.com; one-day pass $24/£18) which, in early spring, is home to the sarus crane. The treacherous road leaves me feeling a little nauseous, but it's worth it to catch a glimpse of the world's tallest bird.
The next morning, I visit La Plantation. Cambodia's prize export is its highly sought-after Kampot peppercorn, and La Plantation is one of the largest organic farms in the region. A private tour concludes with a novel experience - a pepper tasting. I take on a hearty meal at the farm's restaurant, trying Kampot pepper on everything from ribs and chicken, to eggplant amok (kampotpepper.com; private tour $6/£4.50 per person).
After a few hours' drive, I arrive at a jetty facing into the Bay of Kompong Song. My destination is the opulent Six Senses on Krabey Island which is accessible only via private speedboat, which takes 30 minutes. I'm welcomed on arrival by an entourage of butlers, who whisk me through the island's jungle interior towards my decadent and palatial private villa. I'm spoiled by the size of the bed, the gorgeousness of the bathtub and, oh yes, my own private swimming pool.
I have just enough time to sample the restaurant, which uses ingredients grown on the island's own organic farm, and the spa, a truly five-star experience that tops off my all-too-brief stay.
The next day, I'm back in the speedboat and en-route to the neighbouring island of Koh Russey, to spend one night at its modular modern masterpiece, Alila Villas. This quiet, minimalist resort has a monopoly of some of the best ocean views in Cambodia.
The next morning, I head back over the bay to Sihanoukville and catch a 45-minute flight to Siem Reap. Cambodia's ancient capital, the temple city of Angkor, is a short drive away. An Angkor Pass (only available from the official ticket centre, $62/£48) offers unlimited access to every Angkor temple.
As is tradition, we start our journey with a sunrise visit to Angkor Wat. While beautiful beyond compare, I would advise bracing yourself before visiting Angkor Wat, as no matter what time of day you visit, you will have to wade through legions of other visitors for your chance to experience this incredible temple.
Thankfully, Angkor Wat is just one of the dozens of temples in Angkor, and it isn't long until I find one more to my taste: Banteay Srei. While no way comparable in size, this intimate temple invites visitors to get up close and personal with its carvings and reliefs.
On the final day, I arrive at Ta Phrom. It may be known locally as the 'Tomb Raider temple' (Angelina Jolie is a big deal in Cambodia), but the experience is in no way Hollywood. Instead, the displays of nature are a reminder Cambodia is home to authentic jungle adventures.
Audley Travel (audleytravel.com; 01993 838 100) offers tailor-made trips to Vietnam and Cambodia from £3,495 per person for 14 nights, including international flights with Vietnam Airways.