as above head to Ranong via mini bus from Lanta to krabi bus station an than local bus to Ranong ( 7-9 hours total ) long tail boat across to Kwathoung Burma<$10 to stamp in an out of Burma.
Back to Thailand< Boat is 50 baht/seat one way or 500 baht/boat r/t
easy and than head to Samui...
PS: Immigration wont let ya depart if they wont let ya back in 🙂