The World's Most Venomous Animal Is ... Thailand's Box Jellyfish
This headline is not really fair on Thailand.
Box Jellyfish know no borders and live throughout the Indo-Pacific region.
Lists tabling 'The World's Most Venomous Animal' or 'The World's Most Poisonous Creature' go a long way in perpetuating the myth that the most lethal Box Jellyfish is solely Australian owned and made. Australian snakes and spiders and marine creatures have a notorious reputation making them a hugely popular topic in school projects and a major point of discussion when planning a holiday. For all the right reasons Chironex fleckeri sits on top of the list but Chironex is as much of a problem if not more so for a suite of South-East Asian countries including Thailand, Malaysia, Philippines and Indonesia.
The Chironex Box Jellyfish in Thailand and Malaysia and the Philippines and Indonesia is proven and documented to kill a human in a matter of seconds - the same as the Chironex in Australia. Specimens and images show that they are all Cubozoan/Chirodropid/Chironex type species.
The difference appears to be that Australia addressed their lethal Box Jellyfish problem decades ago in an effort to save lives, stem the flow of injuries, improve safety on the beaches, etc.
Learning about the animal in their own backyard brought its potency to the world's attention and somehow gave Australia ownership while the same animal kept going about its business in South-East Asia without any attempt by 'home' countries to learn about it and make any changes. People kept getting killed and seriously injured as they still do today but the ramifications were and are nowhere near as profound as in Australia. 'What are a few deaths here and there when malaria and motorcycles kill 1000s and 1000s?'
With the resources at their disposal and a lucrative tourist industry to protect, Australia may well 'own' the Box Jellyfish whether they like it or not but they have negated its potentially devasting effects by properly managing the problem and running a concerted safety and awareness campaign with successful prevention and treatment programs and strategies that have dramatically cut the number of fatalities and near-fatal stings while watching tourism numbers grow and grow.
Perhaps the baton should be passed to Thailand or the Philippines or any number of other countries in the region. Their Chironex Box Jellyfish is estimated to kill more people in one year than have ever been killed by the Australian Chironex Box Jellyfish in that country's recorded history!
Maybe the only fair answer is the World's Most Venomous Animal is the Indo-Pacific's Chironex Box Jellyfish with fatalities in many countries including Australia, Indonesia, Malaysia, Philippines and Thailand.