We organised everything 2 months in advance, booked our flights for the first 3 months, booked hotels that could be cancelled in 1 month and then wanted to book the rest as we went along.
In the end, our itinerary changed right from the start, and for the rest of the trip we booked everything day by day, which was much better!
You can almost always find accommodation even 1 night in advance, and at least you can decide what you want to do as you go along.
Once we had chosen our destinations, we booked our tickets using Skyscanner, which we used throughout our trip and which really did give us the best prices!
However, make sure you click on a link that takes you directly to the company's website, and not through a service provider. We made the mistake of booking a couple of flights through Booking and they never refunded us the cancelled flights...
To travel to Southeast Asia, you will need a passport valid for at least 6 months.
You will also need a paid visa for some countries, depending on the number of days you are staying - here are the details for a French passport:
Japan and South Korea: No visa required for staying up to 90 days.
The Philippines, Indonesia and Thailand: No visa required for staying up to up to 30 days.
Singapore and Malaysia: No visa required for staying up to up to 90 days.
Vietnam: No visa required for staying up to 45 days.
Cambodia: A visa is required for short-term tourist stays (usually up to 30 days). Price: $36
A few weeks before we left, we consulted our GP to get the medication we needed.
In our first aid kit: Doliprane, Nurofen, bandage, Vogalen, Gaviscon, Smecta, disinfectant, compresses, physiological serum, Spasfon, tweezers, tick tweezers, Biafin, mosquito repellent.
We ended up using a lot of Doliprane, physiological serum and Nurofen!
But we strongly recommend that you bring a good first aid kit, especially if you're going into rural areas.
Vaccinations: We also had our Thetanos booster and Hepatitis A vaccinations (around the 100th mark) with our GP. The doctor also advised us to take a malaria tablet, but we didn't because of the side effects.
We our suitcases aside for this trip, they were really impractical, so I advise you to invest in good backpacks.
We stole our friends' bags and I can recommend the one I had, a Quechua Forclaz 50L:
I don't know if it's still on sale in France, but there are quite a few on vinted!
The great thing about this bag was that it opened "like a suitcase" and not just from the top like most bags. So it's much easier to organise your stuff. It's also one of the cheapest on the market (around $60 new)!
My friend took it on a 3 month road trip to South America, it followed me on a 6 month road trip to Asia and it's still going strong!
As well as bags, I'd advise you to buy an organiser (no more than 20e), and they're a must: they save space and a lot of time.
What to bring in one sentence: A lot of underwear and very little clothing.
You'll have the opportunity to buy lots of clothes and other items once you're there, so bring as little as possible so you don't get overwhelmed because everything you take will have to be worn.
We went with 10kg each and came back with 17kg and 16kg haha (Japan got us).
To find hotels, rely on the ratings on Booking or Airbnb, I really don't take a hotel below 9/10 (or 8 if there's no choice) and I've very rarely been disappointed, there's something for every budget.
We've had very comfortable, well-located hotels for less than 20 euros a night.
And for even less, there are hostels everywhere!
We got everything on Airbnb/Booking, but you can also book locally, especially for longer periods, which is even cheaper!
Don't be fooled by weather forecasts that say it's going to rain all day, but there's only going to be a 10-minute shower in the evening.
Also, make sure you know the right time of year to visit the north, centre, south, east and west of a country, as the weather can be completely different in the same period.
However, you won't be running away from the rain, and that's OK - the showers never last very long.
In general, here's the best time to visit each country:
Japan and South Korea (anything but summer, ideally spring, and winters are very cold)
The Philippines (November-April)
Vietnam (February-April and October-December)
Thailand (November-February)
Singapore (all year round, slightly cooler from November to January)
Malaysia (West Coast: December-February, East Coast: July-September)
Indonesia (May-September)
Cambodia (November-April)