What is the best visa option for a friend sailing into Phuket who wants to stay for 7 months while working on his boat?

I wonder if he'll require a work permit to be a captain in Thailand.

This isn't the right forum. He needs to be talking to the marina manager at yacht Haven marina in Phuket. Rules will be tied to him being skipper of foreign vessel.

There are specific rules about how you enter Thailand by sea as to whether you are the Captain, Crew or a passenger on a boat/ship and they don’t differentiate depending on size of the vessel.

I’d assume he’d be the Captain so there are certain rules about what he could do as regards to leaving without the vessel (if needed to). Best to check at the Phuket town immigration office to see what they’d advise.

On entry via sea and assuming he hasn’t bought a tourist visa and that he’s from a visa exempt allowed country he would get 30 days on arrival and can extend for 30 days. He could leave to Malaysia and re-enter twice in a calendar year to do the same.

However if they are having work done on the boat that prevents them from leaving than it’s best to contact the vessel services department in Phuket Town immigration to see what options are available to them.

The boatyard can give them documentation as to why the vessel can’t leave and get an extension but I’m not not up on what may be available.