Speaking to the Otago Daily Times after the announcement of Mr Thomson's dismissal as chairman, Mr Ryall said it was an "opportunity to draw the line under this problem" and to start looking at the big issues facing health services.
Asked if he was looking at dismissing other board members who had been with Mr Thomson on the original board, or whether he would attempt to put controls on chief executive Brian Rousseau, Mr Ryall said his primary relationship was with the chairman, who was appointed by the minister.
He said repeatedly it was a matter of accountability for the fraud, which was the biggest recorded in the state sector.
Mr Ryall said matters relating to Mr Rousseau were dealt with by the board - "my accountability relationship is with the chair".
The minister also scotched rumours he was about to appoint a chairman across both Otago and Southland boards, saying at this stage he saw a benefit in having two separate chairmen.
It could be some weeks before an appointment is made to the Southland job, which has been vacant since the resignation of Dennis Cairns last December.
Mr Thomson's replacement, Errol Millar, who had previously served on the Southland board, would further strengthen the close working relationships between the boards.
Mr Ryall would not discuss his performance over the dismissal.
When asked for his reaction to the suggestion that he was a new health minister throwing his weight around for the sake of it, he returned to his stock responses about the need for accountability over the fraud and that "action needed to be taken".
He had taken all matters into consideration before making the decision to dismiss Mr Thomson, he said, and would not be drawn on what weight he had given to matters raised by Mr Thomson in his submission over the looming sacking.
Mr Ryall said he had not entered into a slanging match with Mr Thomson and was not going to do so now.
Mr Thomson's submission set out his achievements as chairman, stating Mr Ryall's lack of confidence in him was not based on a full assessment of his years as chairman.
"To base it on the criminal actions of one employee, who set up his fraud before I was even chair despite warnings to those in charge at the time, and to ignore my consistent and publicly recognised record seems quite unfair."
If the minister considered there were other actions Mr Thomson should have taken regarding the fraud, then "in the interests of natural justice" these should have been stated so he could respond to them.
Yesterday, Mr Thomson said his dismissal was probably politically motivated to the extent the minister saw the opportunity to replace a chairman with someone appointed by his administration and at the same time garner political points for taking strong action on behalf of the public.
In doing so, he had judged the local situation "quite badly", and when Mr Thomson refused to resign he had backed himself into a corner.
"The burdensome responsibility of having to treat your minister with respect, whether deserved or not, has been lifted from my shoulders," Mr Thomson said.
In his dismissal letter, Mr Ryall acknowledged Mr Thomson's contribution as chairman of the board and said he appreciated his willingness to work constructively with him on health policy and outcomes for Otago and Southland people.
He was critical, however, over the way Mr Thomson had conducted himself in the past fortnight, in particular comments quoted in the Otago Daily Times that Mr Ryall should have had the courage of his convictions and sacked him.
This had been "inconsistent with the conduct I expect from DHB chairpersons", Mr Ryall said.
Mr Ryall would not say whether the new chairman, Errol Millar, a member appointed to the board by the previous government, was the Government's first choice.
However, Mr Thomson, by deciding to stay on as an elected member as he is entitled to do, may have limited the field.
Boards are limited to 11 members, 7 elected and four appointees, and unless someone had been prepared to stand down, an appointment from within the board was Mr Ryall's only option.
Mr Thomson said his plan was to serve out the rest of his three-year term as an elected member, but "I'm sufficiently realistic to know that in four weeks' time I may feel differently".
He wished Mr Millar all the best in the role.
"He has significant experience in health governance and will, I am sure, make an excellent chair."
In other developments yesterday, Speaker of the House Lockwood Smith ruled against a request for a snap parliamentary debate on Mr Ryall's dismissal decision from Dunedin North MP and former Labour health minister Pete Hodgson.
Mr Smith said it was a matter of governance change, where the chairman was being replaced by another member of the board.
In a statement issued later, Mr Hodgson said Mr Ryall's "breathtaking arrogance in sacking someone who helped bring to justice fraudsters should give the entire health sector cause for concern".
Dunedin South MP Clare Curran said a straw poll of key health-related community organisations in Dunedin showed they were shocked and distressed at "Mr Thomson's unfair sacking" yesterday.
