Mr Straka was taken to Patong Hospital with serious head injuries around 1am, and later died in hospital. He was visiting Phuket with his girlfriend, also from Finland.
The Finnish Embassy has been informed of the death.
Paul Edden, team leader for the Kamala Police Volunteers, said witnesses told him when he arrived at the scene that Mr Straka was crossing the main road in Kamala to go to the ATM at Tesco Lotus.
When he walked back across the road, he was hit by a car.
"[Mr Straka] was wearing a white shirt, the road was well-illuminated, and there was little traffic. THe car should have avoided him with ease," Mr Edden said.
The driver was being questioned by Kamala police as the investigation continues.