The Samui Mermaid Resort, Bang Rak
The resort has 78 rooms and a whole bunch of them are located at the 'other side' of the road, near their excellent restaurant. Here the rooms are very cheap, ranging from 400,-THB to 600,-THB per night, pending on the season. There's a pool at this side of the road as well but it's directly at the end/beginning of the airports landing strip, so ideal for early risers.
The room sat the ocean side are more expensive but still very cheap considering the location and you won't pay a lot over 2.000,-THB in any of the rooms. This isde also has a pool and it's own restaurant.
If you need to catch a ferry or are just transiting on Samui, this is the ideal place to stay, cheap and convenient.
Booking by Agoda
Booking by Hotels Combined
Standard room at the airport side