these three countries have common ties that date back over two thousand years and have many things in common.
Cambodia, once the centre of the ancient Khmer Empire, which ruled a huge area that included parts of both Thailand and Vietnam.
It is one of the most popular tourist destinations on the peninsula, despite only having been open to tourism for around two decades.
Filled with stunning landscapes and ancient temples, including the most famous temple complex in the world at Angkor, Cambodia is an amazing place to visit.
Vietnam has also only become a popular place to visit in the last 20 years, following a long and drawn out war that finally ended with the reunification of the country under one government.
From the mountainous region of the north to the 100 islands region in the south of the country, Vietnam has fast become a top place to visit in Indochina.
Thailand, on the other hand, has long been a popular tourist destination, with its tropical beaches and glittering temples, as well as the stunning metropolis that is Bangkok, the capital of this ancient nation.
Formerly called Siam, it is known in tourist circles as the Land of Smiles, and the people are friendly and pleasant, and the food is one of the most popular Asian cuisines in the world.
When planning a tour of these three Southeast Asian nations, it is essential to know the requirements for travel and how to obtain visas for each country.
Visa requirements, while essentially similar in all countries around the world, have their subtle differences in some Asian nations, and before you travel, you need to know how to apply for the visa, and whether you can get it on arrival or need to apply before you travel.
Thailand has one of the easiest visa policies of all the Southeast Asian nations, and getting in is simple.
Many travellers do not even need to apply for a visa to get into Thailand for periods of 30 and 90 days, which makes travelling there even easier.
For those who need a visa for their stay, it can be arranged beforehand through any of the Thai embassies of consular offices around the world, either in your home country or your country of residence or temporary stay.
Visas usually take three days to process, cost around 2,000 baht (US$ 39) and are normally for a period of 60 days from the date of entry.
This can be extended by another 30 days maximum at the Immigration Bureau in Bangkok for around 1,900 baht, or 36 US dollars.
Citizens of 44 nations have the ability to travel to Thailand without the need for a visa for periods of up to 30 days, which can be used twice in any calendar year.
Those visa-free countries include the United States, the United Kingdom, Canada, Australia, most of the European countries, and several Asian countries.
Many of these nations also have the option of extending their stay for up to 30 days by applying for a visa whilst in Thailand.
Chinese nationals, Indian nationals, and a few other countries are required to have the visa arrange prior to travelling to Thailand, or arrange the visa on their arrival at the border or airport.
Cambodia also has simple visa requirements, in order to better facilitate tourism in the country.
Visas can be applied for at any of the Cambodian embassies or consular offices worldwide, or you can make your application on your arrival at the border or airport, which is more popular.
The standard 30-day tourist visa costs around US$ 30, from either the embassy or at the entry port, although if you do not have a photo for the visa, it will cost an extra two dollars.
The Visa On Arrival is available at the major Cambodian airports, as well as several of the overland border checkpoints, but it is important to check which overland borders have the service.
The requirements for the Visa On Arrival are the same as through an embassy, and the cost is the same as well.
The latest option for a visa for Cambodia is the E-visa, which can be applied for online from anywhere in the world, although the list of eligible countries is still limited.
The E-visa costs the same as a normal visa, and allows you to receive the visa as a .pdf document by email, which you can print and show at the entry port.
However, the E-visa is only valid for entry through the airports at Phnom Penh and Siem Reap at present.
Visas for Vietnam can sometimes be a little complex and are constantly changing, so it is essential to know what the right requirements are.
At present, there is no actual E-visa that allows you to get the visa online before travelling, and the Visa On Arrival is a little different than most people are used to.
Visas can be obtained through the embassies and consular offices, and if you are not in your resident country, you just need to show proof of residence in your home country, such as a bill or your passport.
The Visa On Arrival is done by first processing your visa application online, and paying the US$ 30 fee through the secure payment portal by credit card or PayPal.
Once you have done this, you will be sent a visa authorization letter, which you will show to the Immigration Desk when you arrive at your port of entry.
The immigration officials will then issue your visa, and you can enter the country.
However, the Visa On Arrival application must be done online beforehand, and can only be used at one of the six international airports across the country.
How to get there
Flights to all three countries can be found easily enough, though some may require connections in other Asian countries before getting to your destination.
Vietnam does have a few international flights from some countries outside Asia, as does Thailand, while Cambodia only has international flights within the Asian countries.
Flights between the countries can be obtained easily, and are mostly direct flights that are relatively cheap.
Flights between Cambodia and Vietnam can cost as little as US$ 44, while flights between Thailand and Cambodia or Vietnam cost from around US$ 50.
Flying between the countries is the easiest way to travel, as it is faster and simpler than travelling overland. And while you are able to get a visa on arrival in Cambodia and Thailand, you will need the pre-approved visa or the pre-applied visa to enter Vietnam.
Traveling overland between the countries can be done easily, and while it is often cheaper than traveling by flight, it is a lot longer, as there are often long bus trips required to get to the border crossings.
There are five border crossings between Cambodia and Vietnam, although there are only two that are easy to reach and of benefit to international travellers.
All the border crossings from Vietnam to Cambodia have the Visa On Arrival service, which makes it easy to obtain the visa, though going the other way into Vietnam from Cambodia does require the visa in advance from the embassy or consular office.
When travelling overland to Thailand, there are six crossing points between Thailand and Cambodia.
Almost all of these have the Visa On Arrival service if you need it, and for those with a visa-exempt period, any border crossing point can be used. The crossing at Aranyprathet/Poipet is the most popular and easiest to get to from Cambodia.
However, there are no overland border crossing points from Vietnam to Thailand, and you will have to take the flight, or travel through Cambodia or Laos to get there overland.
You can read here a sample 2-week itinerary to visit Vietnam
Best time to visit:
While the climate of Thailand varies throughout the year (it is a monsoon country), it is possible to visit all year round, as there is really no period when the country is closed for tourism.
For most people, the best time to travel in Thailand is from November to early April, when the country is cooler and dry.
However, the country is divided between east and west when it comes to climate, and there are specific times for the best time to travel for each area.
In the east, the climate is good for most of the year, with the lowest rain falling in January and February when it is hottest, and the heaviest rain in November.
In the west of the country, along the coast which is popular for diving and snorkeling, the winter months from December to January are the best, while the monsoon months from July to September should be avoided due to the heavy rains.
February to May is the hottest time of the year, and temperatures can reach as high as 38 degrees on the coast.
You can check here our top list of the best hotels in Bangkok.
Cambodia has a simple weather system that is prevalent across the country, and rarely changes from year to year.
The wet season runs from May to late September, and is best avoided as the road system across the country is subject to blockages in the remote areas due to mudslides and floods.
The dry season from October to April is the best time to travel, though if you are not used to the intense tropical heat, February to April should be avoided.
From October to the end of January, the climate is cooler, and rarely sees any rain, making it the ideal time to travel.
The climate in Vietnam is very varied, with huge differences in climate from north to south.
With three separate microclimates in the country, there are different best times to visit, depending on where you are going.
In the north, the best time to visit is from February to April and August to October, when the weather is relatively mild and dry, due to the high mountains.
In the central region, the best time is from October to February, when there is little rain and the weather is cooler, while in the south the best time to travel is from March to June and September to October.
The peak season for Vietnam tourism usually runs from October to February, when the majority of the weather is cool and dry.
A guest post of Stephanie Lee.