She's a mother on a mission, prepared to return to Thailand time and again if necessary to achieve justice and an end to needless tragedies.
Ms Cooper's 19-year-old son, Felix, was killed in a bus crash north of Phuket in 2010, largely because the vehicle had bald tyres and Felix was thrown from his seat on impact.
Since then, Ms Cooper has been keen to see action taken against the driver and the bus company, and campaigning for changes to make sure other parents are not left to grieve in future.
British Foreign Office and embassy officials have already been told that she and other parents want road safety to be a higher priority in travel warnings.
''What's odd is that embassy travel advisories highlight war zones where people seldom travel and treat the important information about road safety conditions in Thailand, where many more people are killed, as somehow less significant,'' she said.
Ms Cooper says that after undertaking research and talking to authorities in Britain and in Thailand, she believes the road toll for Thailand is much higher than official figures reveal. She also has been told that the chances of a visitor being killed on Thailand's roads are 2.5 times greater than for a resident.
Supporting Ms Cooper in her mission have been a number of Thai officials and academics who agree with her and argue that Thailand isn't doing enough to make its roads safe.
In Ranong this week for the court appearance of the bus driver, Ms Cooper met with Colonel Wanchai Eakpornpit, the man behind Phuket's ''100% helmet'' campaign, who was transferred north after being acclaimed as Phuketwan's Phuket Person of the Year for 2010.
Colonel Wanchai says he hopes Thailand goes ahead with plans to introduce legislation this year that would make seat belts compulsory on buses.
The driver of the bus involved in the crash in which Felix Cooper was killed fled the scene and was not arrested until March.
Earlier this week, Rachel Cooper saw him brought into Ranong Provincial Court in shackles.
On a previous visit to Thailand, she'd found the bus still on its side at the crash scene, and noted the bald tyres.
''The bus would not have been allowed on the road in most other places,'' she said.
Ms Cooper had hoped to be able to say something in court, but this week the bus driver's trial was postponed until June.
Meanwhile, Ms Cooper and her son Louie, 25, will be pursuing answers in her campaign for better road safety in Thailand. Today they are joining the Long Slow Walk in Bangkok on behalf of pedestrian safety.
Phuketwan interviewed Ms Cooper in Ranong at length and will publish an update on her campaign tomorrow.