Andrew Apperley, 38, from Eastbourne, was reported missing after failing to return to his hotel four days after going to the Full Moon party.
Formal identification has not yet taken place but Mr Apperley's family, from Gloucester, have been informed.
"The circumstances of the death are unknown at this time," said a Gloucestershire Police spokesperson.
Mr Apperley was staying at a hotel in Bophut and went to the full moon party on 12 February. He has not been heard from since.
He told his mother he would be returning the following morning, but the hotel reported him missing four days later.
A spokesman for Gloucestershire Police said: "Following inquiries with the Foreign and Commonwealth Office (FCO) we can confirm that a body has been found in the search for Andrew Apperley.
"Our thoughts are with Andrew's friends and family."
Mr Apperley had flown into Ko Samui from Bangkok to go to the party in Ko Phangan, his brother told the BBC.
Richard Apperley said his brother checked in on the morning of the party and left his passport and driving licence with the hotel reception.
Before going out Andrew had a conversation with his mother Linda on the messaging app WhatsApp and said he would be be getting the boat back to the hotel the following morning.
Staff at the Hotel ibis Samui Bophut confirmed earlier he had still not been seen and his documents were still in their possession.
His bank told his family his cards had not been used since going to the party.
Mrs Apperley sent a message to her son's mobile phone, but did not get a delivery report to say he had received it.
Speaking before the body was discovered, a spokeswoman for the FCO said: "We are providing support to the family of a British national who has been reported missing in Thailand.
"We are in contact with local authorities."
A body has been found during the search for a British tourist who disappeared after a beach party in Thailand.