Renting a house instead of a hotel in Thailand is an exciting option, although possibilities are not as widespread as in, for example, Indonesia.  However, staying in your own home is generally much more rewarding than a hotel-based holiday. 

Research opportunities beforehand, and do try to book directly (full pre-payment is required so ensure the house is of quality and you are comfortable that you get what you paid for by searching for the management company).

Particularly recommended for those who wish to get away from the major tourist centres, looking for  personalized service (as most houses have their own in villa employee).

Advantages:
live a dream in having your "own home" on the beach

lower effective cost per person, especially when travelling as 2 or more.
better and more spacious accommodation and facilities
ultimate privacy

encountering the locals
lower daily cost of life as usually all incidentals (F&B items) are at cost unlike in the hotel

Disadvantages:
some villas can be very large (6 to 9 berooms!) so need to put a group together (some large houses offer reduced occupancy rates though).
usually villas have a minimum stay of 3 to 5 days, some can be up to 1 week
not all villas are child friendly, ensure the one you choose is (especially for villas in the hills)

Great for:
wedding (privacy), some villas have gournd for parties of 20 to 80 Guests
Family  reunion and big birthdays
Honeymoon (especially in some resorts as well)
Executive corporate retreat

Examples: (please add as you come across them!)
Gecko Villa : ww.geckovilla.com
Samui Villas & Homes : ww.samuivillasandhomes.com

Fabulous luxury Villas & Bungalows www.thailandholidayhomes.co.uk