It is not a myth.
This article is from 2018, but there are many more, including from the BP. A quick search turns them up.
At least 10,794 lives have already been claimed this year, highlighted Dr Taejing Siripanich, secretary-general of the Don’t Drive Drunk Foundation.
That figure is not a full count of the dead, Taejing said yesterday. It is based on statistics compiled between January 1 and October 21, and takes into account only deaths recorded at the actual accident scene.
“This means road fatalities are actually higher because some victims succumb to injuries later in hospital.”
https://www.nationthailand.com/in-focus/30356972