Tony Rucinski was suspended as head of the Board of Community Health Councils (CHCs) in February 2016.
Two senior officers are working in "acting chief executive" roles.
The board said it had nothing to add to a statement made by its chairwoman last month, which acknowledged an ongoing personnel process.
Dr Rucinski remains suspended on full pay. The role carries a salary of £90,000.
The details of the extra expenditure were revealed in a response to a freedom of information request from BBC Wales.
But the board has declined to put a figure on legal costs as a result of the suspension.
The reasons for Dr Rucinski suspension have not been given publicly. Alyson Thomas and Clare Jenkins are serving as acting joint-chief executives.
The Board of CHCs said: "The total additional salary costs incurred as a result of Mr Rucinski's suspension are £53,511 to the end of January 2017."
But the organisation said it "does not hold information" on the cost of legal services or the cost of the personnel process "in a format that would allow it to calculate the costs incurred as a result of the suspension, nor does it hold information that would allow it to give an estimate of such cost".
The organisation describes itself as the "independent voice of patients" in Wales.
It and the seven CHCs it oversees had an annual budget in 2015-16 of £3.8m.
Dr Rucinski was appointed as chief executive of the board in a newly-created role in July 2015.
At the time, he told BBC Wales he had been "put in place to make things happen".
Four months later the Welsh Government appointed Ms Merrill as the board's new chairwoman. Dr Rucinski was then suspended in February 2016.
Several sources have told BBC Wales there was tension between Dr Rucinski and Ms Merrill prior to his suspension.
In January, employment lawyer Damian Phillips said it was an "extraordinary period of time to suspend an employee".
In the statement made last month, the board's chairwoman said: "I can confirm on behalf of the Board of Community Health Councils in Wales that there are ongoing personnel processes relating to the chief executive officer and due process is being followed in respect of those matters."
The suspension of the chief executive of the patients' watchdog has cost more than £53,000 in extra salary payments.