At a packed press conference, the media witnessed a ceremonial handover of SWFC from Milan Mandaric to Dejphon.
Following an introductory speech from the outgoing chairman, journalists posed a raft of questions to Dejphon ranging from his reasons for assuming full control of the club to his immediate and long term ambitions, the club reported on its website www.swfc.co.uk.
Dejphon said: "I want to get Sheffield Wednesday back in the Premier League and make the supporters of this club proud.
"This club is steeped in history and tradition and will soon be celebrating its 150th anniversary in 2017.
"I would like that year to coincide with a return to the Premier League and celebrate the two together.
"I promise the supporters I will do the very best within my powers to get this club back where it belongs."
Sheffield Wednesday, one of England's oldest football clubs, last played in the Premier League 15 years ago.
Mandaric added: "Straight away after meeting Mr Chansiri, I knew I was dealing with a winner. He has enthusiasm for this job and I am confident he will be a top chairman.
"I am not getting the champagne out or anything like that because as I have said before, I am not desperate to leave this wonderful club.
"But as I always said, if someone can come along and accelerate the process to take Sheffield Wednesday into the Premier League, I would step aside.
"That time has now arrived."
The Owls are the third English club owned by Thais along with Premier League side Leicester City and Championship team Reading. Bangkok Post