South of Ko Lanta the province of Trang remains more tranquil then the rest of the Andaman Coast, even in high season. There are still some beautiful islands off shore and plenty of attractions in land at day trip distance.
Trang is some old school Thailand. If you want to get off the beaten track a bit, check into the Hotel Lawanna, get some grub at the night market, and enjoy no one speaking english or german. I kinda liked it, but a few years ago it was pretty rustic, even the tuk-tuks looked older. Great food to be had, and you can catch a bus to the shore to get to Koh Muk, or elsewhere.