Train 86 from Surat Thani to Hua Lamphong Railway Station in Bangkok is an Express service with a wide range of seating and sleeper beds available, from 3rd, to 2nd and 1st class.
3rd class seat in a fan cooled carriage:
Adult Fare: 257 THB
Child Fare: 204 THB
2nd class seat in a fan cooled carriage:
Adult Fare: 398 THB
Child Fare: 274 THB
2nd class bed / berth in a Day & Night air-conditioned carriage:
Upper Berth: 668 Baht
Lower Berth: 718 Baht
Upper Berth: 544 Baht
Lower Berth: 594 Baht
1st class bed / berth in a Day & Night air-conditioned carriage:
Upper Berth: 1139 Baht
Lower Berth: 1339 Baht
Upper Berth: 880 Baht
Lower Berth: 1080 Baht
3rd class seats are the cheapest way to travel from Surat Thani to Bangkok, but for this long overnight journey not recommended if you want to get some sleep.
The reclining seats in 2nd class seat carriages are much more comfortable and the coaches are less crowded and quieter the 3rd class
For a decent nights rest, the 2nd class sleepers are the best choice.
If you have a choice, book the lower berths as they are much wider and much more comfortable than the upper berths (they also sell out first).
On this service they are all air-conditioned coaches, so bring something warm to wear as they can be quite cold at times.
If you want to splash out, 1st class cabins are available, sleeping two passengers in each cabin.
You can even book a cabin for sole occupancy if you want.
Unless you travel 3rd class, you should book your tickets as far in advance as you can to get a good sleeping berth or 2nd class seat.
To book advance train tickets in Thailand you can:
1) Visit any SRT railway station and buy your tickets in person.