The creature looks like it's a proboscis or ribbon worm, Kyle Hill of Nerdist explains - a Google translation of the video description from Thai to English seems to indicate the same.
When these worms 'mouth fight', a short proboscis extends followed by extremely rapid expansion of the posterior pharynx. This rapid strike produces a loud 'pop' comparable to those made by ...
Watch: The Rich in U.S. Are Freezing Themselves to Stay Wealthy Forever The proboscis of the blood worm shoots out and ensnares its prey. However, the worm is not known to go after humans.