BANGKOK - Thailand's former foreign minister and Asean secretary-general Surin Pitsuwan died on Thursday (Nov 30) afternoon from a heart attack.

The 68-year-old politician, who chaired the think-tank Future Innovative Thailand Institute, was due to give a speech on Thursday afternoon at a halal convention in Bangkok. He is survived by his wife and three children.

Dr Surin, the former deputy leader of the Democrat Party, was a prominent Muslim figure in his home country as well as one of Asean's most eloquent advocates.

In an interview with The Straits Times in 2013 about Thailand's political situation, the Harvard-educated politician said: "A lot of people are reaching the conclusion that this country needs some new answers to solve old problems. I think there is a need for someone to be leading them to think and to ask those important questions."

With the coup-installed military government now past its third year of rule, Dr Surin announced in June he wanted to run for Bangkok governor, as soon as local elections resumed.

"I am not interested in running for Bangkok governor only to win the post, but I want to show that defence of democracy is possible," he was quoted by Bangkok Post as saying. "If we can reform Bangkok, we can also reform Thailand."

His sudden death was greeted with shock by another former Asean secretary-general, Mr Ong Keng Yong, who had arranged to meet Dr Surin to talk about Asean developments in Singapore on Friday.

Mr Ong, who is now executive deputy chairman of the S.Rajaratnam School of International Studies, described Dr Surin as a humanitarian at heart.

"He was always concerned about how people were treated, and how they could fend for themselves," he told The Straits Times. Dr Surin, he said, was "familiar with western political philosophy while a South-east Asian at heart".

He was both persuasive as well as true to his convictions.

"He did not break the way Asean works although he could not agree with all the political decisions in Asean," Mr Ong said.

The outspoken Dr Surin found ways to work with the 10-nation bloc's consensus style of decision-making. Under his helm, Asean sped up aid to Cyclone Nargis survivors in military-run Myanmar in 2008 by coordinating the supplies contributed by international aid agencies.

More recently, he urged Asean to step up in the wake of Myanmar's Rakhine crisis, where an insurgent attack in August was met by a military crackdown which is now being likened to ethnic cleansing of the country's Rohingya Muslims.

Asean, he wrote in a commentary in September "will have to act fast to save lives and prevent the carnage from deteriorating and escalating into regional tensions".

"The world is watching," he wrote. "Asean's credibility and profile are hanging in the balance."

The Asean secretariat said his death was "a big loss to Thailand and the Asean community".

Thailand's foreign ministry in a statement said Mr Surin contributed greatly to the advancement and interest of Asean, as well as the promotion of Asean on the international stage.

"His outstanding personality, knowledge and wisdom were truly recognised by global leaders," it said.