After getting out of the taxi at Suvarnabhumi, I thought I left something inside the taxi," he told Tourist Police. He thought he saw the cab about to leave and walked back to it, unaware it was a different taxi.
"The car didn't stop so I shouted at the driver and hit the boot," Mr Lucas said.
The Australian said the driver got out of the car and hit him on the head, knocking him to the ground.
Mr Lucas said he was due to catch a flight to Australia to attend his grandmother's funeral, but missed it as a result of the assault.
Police later summoned 32-year-old cabbie Kamphan (surname not given), who confessed that he attacked Mr Lucas.
"I was angry that he tried to open the door and hit the boot. My wife was sitting in the car and I was concerned for our safety," the driver said.
Police charged Mr Kamphan with physical assault causing injury. However, he may face more charges if the Australian has to receive medical treatment for more than 15 days.