Depending on when you travel, you might be able to get a three bedroom villa at Karma Samui for ~$700 a night. They used to be a member of LHW and would offer very low rates on lhw.com. Unfortunately they are no longer affiliated with LHW, and the rack rates on their website seem quite high.

If you are interested in Karma, I would recommend that you contact the reservation manager and try to negotiate a rate. karmasamui.com