Witnesses told police that two suspects walked into Ms Sumittra’s house, with one of the men shooting her in her head while she was watching television.
CCTV camera footage shows that the suspects came in a pickup truck, which was parked opposite the See Koa fresh market, 500 metres from where the murder took place, before they walked to Ms Sumittra’s house.
After the shooting, police radioed Tha Chat Chai checkpoint to be on the lookout for the pickup.
The two suspects were later arrested along with the alleged getaway driver the driver.
The three were identified as Aroon Pantarn, 28, Sawit Jongrak, 28, and Sanguan Poongen, 26. The trio are all from Krabi province.
After being questioned, the three initially denied any involvement in the murder and said they were in Phuket to visit their friend.
However, they later admitted that they were hired by a Thai woman suspected to be the wife of Ms Sumittra’s British boyfriend.
The suspects told police that they had been paid B40,000 as a first installment, with a further B40,000 to be paid once they had successfully fled Phuket.
After the shooting, at which Sawit was the suspected assassin, the three dumped their shirts and a .22 caliber gun on the north side of the bypass road.
According to police investigation, the British man often visited Ms Sumittra at her house when he was in Phuket.
They had been in a relationship for approximately two years before the murder yesterday.
Police are still looking for the Thai woman suspected of ordering the hit.