Upvote:2
I visited the Andamans some time ago and looked into this. As far as I am aware, there are no direct connections of any kind between the Andamans and Thailand, not even by airplane.
This is kind of absurd since Thailand is actually closer to the islands than mainland India, but at the end of day it's geopolitics (different country) and economics (the islands are quite small and poor by world standards, and demand for international travel to them is low).