Lekpet Prasert, 48, the driver of the taxi van was slightly injured and was detained for questioning after he admitted to driving over 120 kilometers an hour on the expressway.
The incident happened on the expressway in front of the Bangkok International Trade and Exhibition Center on at about 7.30 pm.
The taxi van started from the Victory Monument on its way to Sri Racha with 14 passengers.
According to PBS News the driver, he drove at 120 kilometres an hour while the van was approaching the “S 1” curve on expressway in front of the Bangchak oil depot.
Suddenly the van lost balance and ploughed into the concrete barrier and flipped over in front of the exhibition centre.
Four passengers, three of them women, died on the spot and 10 others injured.
No other vehicle was engaged in the crash.
A wounded passenger Yingyai Tochaiyaphum, 59, said that the driver asked to stop for tyre replacement for about an hour on the expressway after saying a tyre was leaking air.
After having the leaked tire replaced, he drove off again but at unusually high speed, he said.
Before approaching a curve, the van swayed right and left before crashing into the barrier and turned over, killing four people who included his girlfriend, he added.
The driver was detained and initially charged with reckless driving before more charges would be filed against him.
The fatal accident forced expressway authorities to close three outbound lanes on the expressway, leaving only one lane open to traffic, causing heavy traffic congestion last night.
Meanwhile in Lampang, 4 Myanmar workers and the Thai driver were killed when their pickup truck was struck by an 18-wheel trailer truck whose driver fell asleep driving along a road in Ngao district overnight.
Ngao police investigator Pol Lt Jakkarat Tanburawong said Somkid Roongpaopan, 37, was driving a trailer truck loaded with corn along the two-lane Ngao-Song Road early on Tuesday morning. He dozed off at the wheel and his vehicle ran head-on into a Bangkok-registered pickup truck in the opposite lane.
The pickup driver, identified as Siam Pinthong 31, and two Myanmar migrant workers, a man and a woman, died on the spot. Six other Myanmar workers on the pickup were injured and taken to Ngao hospital, where two succumbed to their injuries.
A surviving passenger said he saw the truck veering from side to side across the road before the collision.
Mr Somkid, from Petchabun, told police he simply blacked out. The truck overturned and he became aware of what had happened only when rescue workers pulled him out of the vehicle. He was unhurt and surrendered to police after the crash.
The long-haul truck driver admitted he had not had enough sleep for several days as he was trying to meet the deadline in transporting corn from the northern province of Phayao to the central provinces.
He was arrested and charged with reckless driving causing deaths.