You would have probably read a lot of reviews about the trains that said "bring extra layers it's cold at night"... Well as soon as you walk on the train you start shivering and rummaging round tour bags for jumpers and socks. Everyone that walked on said "Woah I know they said it was cold but" ... The temperature inside is 21 degrees.
the seats on the train are big and comfy you could almost fit 2 people on each seat (you wouldn't but you could as there is enough room)
we bought food on the train, we ordered from the set menu and it was 210baht each. You get 2 x different main courses, 1 soup, 1 rice, some fruit and a banana cake for that price. The food is ok and filling and warms you up! Although they did say nothing was spicy and the Duck Red curry was incredibly spicy... You could buy breakfast on the train too at (I think) 170 baht each but we didn't buy it.
The guard comes round about 8pm to do the beds,he's so quick and very efficient. Beds are comfy, the top and bottom bunk "sleeping matts" are the same width but the bottom bunk does have some extra space towards the wall. The top bunk is a lot colder as the A/C is closer and is also a lot brighter as you're closer to the lights.
the toilets are cleaned regularly throughout the journey and they come through and clean and mop the floors in the carriages as well which is nice.
the train itself is silent, the only noise is from the wheels on the tracks. The lights in the carriages aren't dimmed at any stage throughout the night.
the guard comes and Wales you up at 6am so he can turn the beds down- they then bring breakfast round to those that ordered and ask you to check all luggage before leaving the train (I imagine this is in case of any theft throughout the night). i slept with my "hand lugggae" size backpack in the bed but left my big rucksake under the bottom bunk and it was safe all night. there is room under both seats to place suitcases of all sizes (if pushed under from the front if that makes sense, where your feet go effectively) and no one will get them out easily from the side- into the walkway- when the beds made as that area has a smaller gap under the seats.. This may not make sense but it will when you're on the train!:)
all in all it was a great experience and I would do it again! :)