On track at last ... the new railway line runs over the Thai-Laos Friendship Bridge. Photograph: Nik Wheeler/Corbis
Next week, Laos will be connected to the outside world for the first time by rail when a new link opens across the Mekong river to Thailand.
Princess Maha Chakri Sirindhorn of Thailand will officially open the line on Thursday 5 March, and the first train to carry passengers in and out of Laos will start running on Friday morning, according to the Thai state railway.
The people of Laos have been waiting a long time for this moment – around two years since the US$6m project first broke ground in 2007, and a year after the line was originally due to open.
The first train will leave Nong Khai in Thailand at 9.10am and arrive at its destination, Tha na Lang, at approximately 9.25am. We are talking about a 3.5km stretch of track here – one that runs over the Mekong, via theFriendship Bridge and connects the existing Thai line to Tha na Lang - its only stop - just outside the Laos capital of Vientiane.
At the moment, Tha Na Lang is just a bright, shiny railway station; there is not much in the way of a village or town or anything else here. Undoubtedly, with the advent of the railway age, this will change as Tha Na Lang will become the preferred jump-off point for visitors to Vientiane, roughly 20 miles up the Mekong – travellers will likely take a tuk-tuk or bus for the short hop into the Laos capital.
Nong Khai, on the Thai side of the Friendship Bridge, is a different matter being a well-established travellers' hub with great guesthouses, a handsome Mekong-side promenade and a run of French colonial architecture.
There are also plans to extend the line into Vientiane but, given the difficulties in opening this tiny stretch of track, that could be many years off yet. What is certain is that travellers will for the first time be able to take the train from the Thai capital to the Laos capital – almost. And the 620km rail journey from Bangkok to Nong Khai is worth making, as it winds its way through Thailand's largest region, Isaan, a vast plateau filled with antiquities, paddy fields and lush forest parks.
Isaan is also the least-visited part of the country – without beaches or luxury resorts and considered backward by the Thai establishment (the area was also a bedrock for Communist Party support during the 1970s) - it has never been given the attention it deserves. Yet, with the opening of the new line, Isaan is expected to become an essential stop for visitors travelling to and from Laos.
Don't come to Isaan expecting anything to move very fast – even the Thai trains that plough their way through this stretch of north-east Thailand have a reputation for moving slowly. Very slowly. By the time I woke up, my train was almost five hours behind schedule. But I was grateful for this tardiness – without it, the landscape of lakes and light that unfurled through the morning mist would have been lost to the night or the Bangkok smog.
Thankfully, given their late running, Thai sleeper trains have a unique configuration that is well suited to lazy lounging. Buy a ticket for the standard second-class service and you'll find the beds lined up length-wise along an open carriage. Each berth - the upper ones fold down from the ceiling, the lower ones, which have windows, are two day-seats slotted together - has a privacy curtain and comes complete with sheets, blanket, pillow and an extra layer of mattress.
This is a much more pleasant way to travel than on Thailand's insanely dangerous roads. The trains are also packed with locals following the decision in the middle of 2008 by Thailand's rail network to offer free third-class travel for Thai nationals on certain routes.
Western travellers pay around 103 Thai Baht (just less than £2) for the journey from Bangkok to Nong Khai, and while a third-class seat might be a tough option for an overnight journey (the second-class sleeper, lower berth, is the advised choice at 750 Thai baht), for day-time travel it's more than adequate.
The Nong Khai line provides plenty of distractions if you want to explore at a more leisurely pace - you could base an entire week's travel on this route if you wanted. From the Bangkok end, your first stop should be the absorbing crumbling temples and antiquities at the UNESCO World Heritage Site of Ayutthaya, Thailand's ancient capital. Spend a night or two here before getting off at Pak Chong to visit the national park ofKhao Yai, another UNESCO site. It's then a short hop to the earthy Isaan city of Nakhon Ratchisima - Korat for short - where you'll find lively markets, the nearby Khmer ruins at Phimai and 10th-century city walls.
Khon Kaen, a couple of hours to the north, is worth a visit if you hanker after Vietnamese food while Udon Thani has a night market that serves some of the best food in the entire region and also provides the jump-off point to visit the archaeological wonders at nearby Ban Chiang - the last UNESCO site on this route.
The final thing to remember is to throw out the timetable - just be prepared for delays and stunning sunrises.