The RSA says the process involved in changing the flag is unnecessarily complicated and costly.
Over the next few weeks Parliament's justice and electoral committee will consider the New Zealand Flag Referendums Bill, reporting back to Parliament by July 19.
RSA chief executive David Moger said the association would take its support for the country's flag to the committee.
He said the RSA's main concern was the process of the decision, which would cost around $26 million.
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"A two question referendum is unnecessary and far too expensive. Our preference is that it should be a simple question up front -- do you want to change the flag?"
The RSA said Anzac day should highlight the importance of keeping the current flag.
Mr Moger said there was no need to change it.
"That is the flag that we have had for the past 100 years, and it's a flag under which tens of thousands of New Zealanders have committed their lives to service and died under it, and that's part of our history and our heritage."