Train 21.25 was delayed due to mechanical problems. Very little information, only that it would take a long long time. People spoke very little english. We changed the tickets to the train of 01.00 that had 15 minuten delay. Bit stressfull alltogerher. Train Bangkok - Chiang Mai week earlier was perfect in time. So maybe it was bad luck.
I've always had great experiences on the trains in Thailand, I love them. This time I booked the sleeper bed (I usually buy 2nd class sleeper fan which I hundred per cent recommend). First of all the train was 1h 30 min late, the bed carriage felt like a fridge: cold and humid and it smelled weird, like humidity. The beds felt moist because of the humidity in the air. Needles to say I barely slept. So I payed extra for "sleeping" in a poorly ventilated fridge. The 2nd class seater fan carriage is way better.
Lots of noise every stop so you wake up about every hour and from about 5 am almost every stop there were vendors boarding the train and trying to sell stuff.
Bathroom was really stinky too
Besides that the bed was fine and we got a clean mattress and pillow with a blanket and the staff and conductors were nice :)
Train was 1 hour late and arrived 4 hours late to Bangkok. Sleeper seats ok, nice to be on horizontal position on a 12 hours trip. Quite noisy night but exciting experience for all of us. Maby train 170 is a slower- one. Train was full so we got sleeper beds around one van. Kids are already teenagers so this wasn't a problem.
2nd class night train does the job, but I'd recommend anyone to book 1st class if they can for a better night's sleep! Booking on 12goasia and receiving the PDF tickets in minutes made the whole trajectory a lot easier.