well if there is fish, they can live until they die, and if there is no fish I am sure there is seaweed.
We are not talking about a scripted movie here to survive in the ocean with fish alone, for water they will bring purifier

, even if they are determined they have to somehow reach some shores to get the essential things for their survival, it is real life with consequences and i am not sure what criminal activities they did to be chased like that.
They should anchor in international waters and not even follow the laws of Thailand.
National security is the card every country will use to put someone behind bars if they cannot find any other law to hold someone back, be it whistle blowers or any other individual who goes beyond the normal criteria and even if they anchor in international waters they will be under custody and it is a matter of time how long they can play this hide and seek.
People live on boats all over the place. Boats are better, because they can easily move to better locations.

Definitely they could have lived in a boat or a yacht peacefully rather than these hurdles

.