The United Nations chief has warned Asia to quit its "addiction" to coal, as climate change threatens hundreds of millions of people vulnerable to rising sea levels across the region.

Key points: UN chief Antonio Guterres told Asia it is "lagging behind" and said the rollback of coal could help curb rising global temperatures

UN chief Antonio Guterres told Asia it is "lagging behind" and said the rollback of coal could help curb rising global temperatures Australia is the world's biggest coal exporter

Australia is the world's biggest coal exporter According to the Minerals Council of Australia, most of Australia's coal production is sold overseas, and mainly to Asia

The warning follows fresh research this week predicting that several Asian megacities, including Bangkok, Ho Chi Minh City and Mumbai, are at risk of extreme flooding linked to global warming.

Antonio Guterres said Asian countries need to cut reliance on coal to tackle the climate crisis, which he called the "defining issue of our time".

Australia is the world's biggest coal exporter, with most Australian coal being sent to Asia.

"There is an addiction to coal that we need to overcome because it remains a major threat in relation to climate change," Mr Guterres told reporters ahead of a meeting of the Association of Southeast Asian Nations (ASEAN) in Bangkok.

He said countries in the region needed to be on "the front line" of the fight by introducing carbon pricing and reforming energy policies.

"We are lagging behind," he said, adding that the rollback of coal could help curb rising global temperatures.

Coal remains a major source of power across South-East Asia, where breakneck economic development has spurred soaring energy demands at a cost to the environment.

About one-third of Vietnam's energy comes from coal power with a slew of new plants set to come online by 2050, while Thailand is investing in fossil fuels.

Coastal areas across South-East Asia have already seen major floods and seawater incursion linked to climate change.

New research this week showed that at least 300 million people worldwide are living in places at risk of inundation by 2050 — a much bleaker picture than previous data predicted.

Destructive storm surges fuelled by increasingly powerful cyclones and rising seas will hit Asia hardest, according to the study in the journal Nature Communications.

AFP/ABC