Yes I went last year and you need to take boat at Koh Samui North and the cost is cheap 15$

Koh Phangan is an island in the Gulf of Thailand, known for its beautiful beaches and the famous Full Moon Party. Here are general guidelines on how to travel to Koh Phangan:

By Air:
Fly to Samui Airport (USM): The nearest airport to Koh Phangan is Samui Airport on Koh Samui.
Ferry from Samui to Koh Phangan: From Samui Airport, you can take a taxi or shuttle to the ferry piers and then catch a ferry to Koh Phangan.
By Train and Bus:
Take a train or bus to Surat Thani: You can take a train or bus to Surat Thani on the mainland of Thailand.
Bus and Ferry Combo: From Surat Thani, take a bus to Donsak Pier and then a ferry to Koh Phangan.
By Bus:
Bus to Surat Thani or Chumphon: Buses run from various locations in Thailand to Surat Thani or Chumphon.
Bus and Ferry Combo: From Surat Thani or Chumphon, take a bus to Donsak Pier and then a ferry to Koh Phangan.
By Car:
Drive to Donsak Pier: If you're driving, you can go to Donsak Pier on the mainland and then take a ferry to Koh Phangan.
Car Ferry: Some car ferries operate between the mainland and Koh Phangan.