Two weeks in Southeast Asia is enough for one country done properly or two done briskly. It is not enough for the Thailand–Laos–Vietnam–Cambodia loop, whatever the forum posts say, unless you are content with a fortnight of bus stations and airport lounges.
The arithmetic that people skip: an internal flight costs half a day door to door, an overnight bus costs a day of usefulness the following morning, and arriving somewhere at 6am with no room until 2pm is not arriving.
Four routes below. Each assumes fourteen nights on the ground, excluding the flights in and out.
Route 1: Northern Thailand and the islands
The classic first trip, and it is popular because it works.
Bangkok, 3 nights. The Grand Palace and Wat Pho on the first morning before the heat, then stop doing temples. Chinatown at night for the food, Wat Arun at sunset, and a long-tail boat on the khlongs to see the version of the city that is still on water.
Chiang Mai, 4 nights. Fly, an hour, rather than the overnight train — though the sleeper is genuinely good if you would rather have the night. Temples in the old city, a cooking course, and a day in the hills. If you want to see elephants, choose an observation-only sanctuary, not one that offers riding or bathing.
Fly south, 6 nights. Krabi and Railay for limestone and climbing, or Koh Lanta for quiet, or Koh Tao if you want to learn to dive.
The season catch: the Andaman coast (Krabi, Phuket, Lanta) is best November to April. The Gulf coast (Koh Tao, Samui, Phangan) runs opposite and is wettest in November. Choose the coast by month, not by preference.
Route 2: Vietnam end to end
Fourteen nights covers Vietnam north to south if you fly once or twice.
Hanoi, 3 nights. The old quarter, which is genuinely chaotic and rewards walking without a destination. Day trip or overnight to Ha Long Bay or, better, the quieter Lan Ha Bay.
Ninh Binh, 1 night. Limestone karsts in flooded rice paddies, a rowing boat through caves, and a fraction of Ha Long’s crowd.
Hue, 2 nights. The imperial citadel and the tombs along the Perfume River.
Hoi An, 3 nights. A preserved trading port with a tailoring industry and the best food in the country. Rent a bicycle and get to the beach.
Fly to Ho Chi Minh City, 3 nights, with a day in the Mekong Delta or at the Cu Chi tunnels.
Two nights spare for a slower pace somewhere, which you will want.
The season catch: Vietnam is three climates. The centre — Hue and Hoi An — floods in October and November. The north is cold and drizzly in January. There is no month when all three are ideal.
Route 3: Cambodia and southern Vietnam
For people who want ruins more than beaches.
Siem Reap, 4 nights. Three days of Angkor on a three-day pass, spread across a wider window, with a rest day. Sunrise once, not three times.
Phnom Penh, 2 nights. The Royal Palace, the National Museum, and Tuol Sleng and Choeung Ek, which are necessary and very hard.
Kampot and Kep, 3 nights. River, pepper farms, crab market, and the abandoned French hill station at Bokor.
Overland to Ho Chi Minh City, 4 nights, with the Mekong Delta.
Route 4: Java and Bali
Indonesia, and the one that shows you volcanoes.
Yogyakarta, 3 nights. Borobudur and Prambanan, two of the great temple complexes in Asia, plus a city with a strong batik and gamelan tradition.
Mount Bromo, 1 night. The 3am start to the viewpoint is worth it.
Ijen, 1 night. The blue flames and the sulphur miners, which is an uncomfortable thing to watch and worth understanding.
Bali, 6 nights. Ubud for two, then somewhere on the coast. Skip the south-west beach strip unless clubs are the point.
Nusa Penida or the Gilis, 3 nights if you would rather have water than culture.
The season catch: Indonesia’s dry season is May to September, which is the opposite of mainland Southeast Asia’s. A trip combining Thailand and Bali in one fortnight always compromises one of them.
What applies to all four
Fly the long legs. AirAsia, VietJet and the rest make internal flights cheap, and a two-hour flight instead of a fourteen-hour bus buys you a day and a half of your fortnight.
Book the first and last nights and improvise the middle. Accommodation is plentiful and cheaper booked a day or two out.
Two nights minimum anywhere. One night means you arrive, sleep, and leave, and you will not remember it.
Leave two nights unallocated. Something will be better than expected, or a bus will not run.