The powerful Phuket politician died in Phuket City at one of his homes suddenly yesterday, aged 70. He was known to suffer from chronic asthma and an enlarged heart.
Khun Pian's body, being autopsied in Surat Thani, will be returned to Phuket tomorrow evening when a period of mourning will begin.
Khun Pian will rest in an open casket at his mansion behind the family's Pisona business offices in Phrabaramee Road until his cremation, which has been set for 2.30pm on October 18.
The ceremony, at Wat Laem Pech, behind the Loma Park football field off Patong's beach road, is expected to attract several thousand mourners.
His unexpected death leaves a void in Patong, the holiday hub he helped to create over four decades as a local powerbroker.
Khun Pian served in the Royal Thai Army from 1965 to 1967 as part of compulsory military service. He stayed on, during the Vietnam War years, from 1967 to 1969.
In 1974, he was elected as village chief of Patong's Moo 3.
With his status as pooyaibaan established over many years, he won office as the chief of the whole of Patong in 1993.
Changes followed as Phuket and Patong grew rapidly and on July 17, 1994, he first became Mayor of Patong.
Success at most elections followed, with Khun Pian serving at Patong Mayor from 1998-2001, 2004-2008, 2008-2012, and 2012 to March 7, 2014, when he lost a rerun to the present mayor, Chalerlak Kebsub.
The downfall of the house of Keesin began last year, when he and his eldest son Prab were named by the Department of Special Investigation in a document listing 11 alleged members of the Phuket ''mafia.''
Three of those named launched defamation suits and Khun Pian, like his son Prab, asked whether the mafia are the people who pay the money, or the people who take it.
''Do these people understand the problems in Patong and Phuket?'' he said. ''Do they understand what is going on? This has been going on for a long time already.
''If you come here, seeking money, you'll get the money. If you come here seeking to fix a problem, you've got a problem.''
At least 14 government agencies are commonly known to take bribes from businesses in Patong.
Efforts by the DSI to sort out Phuket's taxi transport woes achieved minor successes but then quickly dissipated.
It wasn't until the military took charge of Thailand in May this year and Region 8 police with the Army raided and arrested scores of taxi drivers in Kata-Karon, Cherng Talay and Patong that the allegations against the Keesins were raised again.
This time, the allegations involved links to Patong's taxi ''mafia'' and beach chair vendors who in some cases allegedly extorted millions of baht from resorts for illegal use of Phuket's public beaches.
So far, though, specific allegations against the former mayor and his family have yet to be made public. It's likely there will be a halt to revelations and further arrests until after Khun Pian is cremated.
Of his many projects for developing Patong and Phuket, perhaps the greatest of them all, a multi-billion baht tunnel through Patong Hill, will now be left to others to achieve.