This place is a Ko Lanta institution for being one of the few places (if you're not going for toasties) you can get a late night meal. It's open to 3 am, and in the high season sometimes even to 5 am. It's cheap and about as local as you get, seemingly being both their living room and restaurant. They're pretty cheap and has the normal Thai food menu.
Try the crispy pork with kale if they have it. Add a fried egg (kai dao) for even better meal :)