He ignores bloggers' jibes about his haircut and moustache and responds with his trademark good humour, saying he is happy to answer questions from anyone who wants "facts rather than nonsense".
He says he has never been afraid of a fight, happy to "engage in a battle of ideas", but "I have difficulty attacking people just because of who and what they might stand for".
Using wit to "keep everybody from tearing each other's throats out" was something he learned from former area health board chairman Prof Michael Cooper.
Educating people about matters relating to health, often using colourful language and humour, has been a large part of his modus operandi as chairman.
It concerns him that people see health issues in simple black-and-white terms, when it is "enormously messy and grey".
He says that simple view is not helped by much of the media coverage and he has done his best to make journalists he has dealt with aware of the nuances of a complex subject.
He sees one of the difficulties in health communication is that the group that takes the keenest interest in health is generally made up of the over-50s, people who are "getting closer" to needing the services.
Their knowledge of health services can be about 30 years old - from when they had babies. They often still believe everything would be all right if hospitals returned to the time when they were run by matron and the medical superintendent.
Since those days, the scale of operation needed to run hospitals well and safely has altered significantly.
The challenge of the next 10 years is that there will have to be a "fundamental rethink of how and where services get provided".
Otago and Southland have already begun this process with moves towards shared clinical services, but it will be something that the whole nation will face.
Inevitably, there will have to be a trade-off between ease of access and quantity of access, he says.
People will be inclined to think this was all about saving money, and that is part of it, but Mr Thomson says it is more about safety and ensuring that specialisms are clinically sustainable.
It could mean that some services offered in half a dozen places now could only be available in two centres in future.
Parochialism would hopefully be overcome when patients faced with treatment confronted their choices: not having a treatment because it could not be done in Otago; or having it done in Otago where "the risk of something happening is very high"; or having it in Wellington where a service was offering "best-practice" treatment.
Mr Thomson says a debate will be needed about whether future funding in Otago should recognise the need to provide services close to the University of Otago's health sciences division to help sustain it, recognising both its national value and importance to the local economy.
At the moment, board members made decisions about services with that in the back of their minds, but the board was not funded for such consideration.
The closer collaboration between Otago and Southland, in which he worked with his Southland counterpart Dennis Cairns (who stood down late last year), is one of the highlights of Mr Thomson's term as chairman.
He admits it has not always been easy, saying once he thought there might be "one or two homicides" before the first combined-service Southern Blood and Cancer was established in 2007.
However, he and Mr Cairns had always got on well.
There had been arguments and disagreements, but there was always a will to find a way forward.
Both sides had to give from time to time - "it's a bit like a marriage, you've got to be prepared to work at it".
Both boards had begun to recognise that their long-term survival depended on being able to work together.
The seeds of the Southland-Otago collaboration were sown in the Dunstan Hospital project.
It had produced an "enormous amount of goodwill", although Mr Thomson recalls being in an Alexandra hall in front of about 600 people "all believing I had no intention of delivering them a hospital".
Another achievement he is proud of is turning around the board's financial position.
When he became chairman, the board had a $12 million deficit and was overfunded, according to the population-based formula, by $32 million.
He had to work to change the long-held Otago belief the problem was the formula.
Otago had been fighting the formula since 1987, the Ministry of Health did not trust the board, and did not believe the board was sincere in its intention to live within its means.
This also meant ensuring that management and board objectives were the same.
Mr Thomson says this was not a criticism of former chief executive Prof Bill Adam, who had been brought in to repair relationships between management and clinicians.
He had done a brilliant job of that and was the right person for the job at that time.
The later appointment of chief executive Brian Rousseau was important for the savings regime because he was able to come in sure of what the board's expectations were.
In the next five years, the board moved to a break-even position without cutting services.
The board's financial position today has deteriorated, driven by high salary increases beyond its control and funding which did not match that.
The saving of $40 million over 10 years, through what Mr Thomson describes as the first successful amalgamation of hospital and community laboratory services into a single, privately run service, was another highlight.
He has called this a "high-wire act with people yanking on both ends of the wire, hoping we would fall".
He sees his decision-making as empirically driven rather than ideologically based.
He can see circumstances where public and private health providers can work extremely well together and he is all for that, but he urges caution regarding the belief that public hospital elective surgery provision is inefficient and would be better done privately.
"You've no idea how efficient public hospitals could be if only we only dealt with cases booked for surgery and didn't have to stop when the helicopter landed on the roof; if we didn't have to stay open 24/7 even if there is no-one to treat . . ."
The fraud remains the low point of his time on the board and he says there are still many "what-if" questions.
In a farewell letter to staff, Mr Thomson said convicted fraudster and former employee Michael Swann might be the person "smiling widest today, but I will smile wider than him when he is sentenced, I'm sure".
One of his regrets is that integration of community and hospital mental health services since the 2004 mental health review has not progressed as much as he would have liked.
There has been criticism of the board's performance in this area, particularly over its failure to introduce some services expected in 2007.
Mr Thomson says he believes there is now a greater emphasis on building relationships between the board and community providers of mental health services and among community providers themselves.
He hopes even those who might not have supported him have recognised that he has always "given a damn".
The need to "give a damn" is something he has "hammered home" to those responsible for answering complaints letters to the board.
People wanted to know "when we stuff up, as any organisation does from time to time, that we care".
Now his term as chairman has finished Mr Thomson says he has a sense of loss.
He remains a member of the health board and chairman of the hospital advisory committee.
He will have more time for his business, which has grown from two shops to 10 during the time of his chairmanship.
He will continue to chair the Hawksbury Trust, which he helped establish and which caters for 120 adults with intellectual disability in Dunedin and Christchurch and which has been something which has "given me most pleasure over the last 20 years".
His dismissal as chairman meant he had been given his life back, "but I'm not entirely sure how to use it or what to do with it".
