I don't expect anything concrete from ASEAN. Not because it is incapable. It is a very capable and credible organization in one of the world's economic hot zones.
@madokafc is correct to state that it is very important to recognize a nation's sovereignty.
The reason why I stated so is because the issues in Burma are far more deep than a random fire-fight over some temple at the Thai-Cambodian border. So deep that no one can handle it. Not even the U.S. They can barely maintain order in Iraq (another country bogged down by ethnic and sectarian divisions).
There is a question mark though. A month back, there was an attack on a police station killing 9 officer in the state of Rakhine. Surprisingly by Rohingyas. Along with other nuances, had they been illegal immigrants from Bangladesh (as they claim), shouldn't there have been a military response from them against Bangladesh? All I see is a sense of irony in all this.
Bangladesh has a weak policy? There is no policy on earth to locate a certain people due to ethnicity/religion/whatever to another place. The memories of WWII are still fresh among many folks these days. There's nothing we can do really than to just harbor refugees. Do not expect the Thais to do much either. In fact, they had become part of the problem by engaging with the human trafficking business. Getting a Thai visa for Bangladeshis is much more difficult now. Now that says a lot.
So what is our solution? Well, we have to ask ourselves as to what threats we face. No, the threat is not the Burmese military. The threat stems from the violent third parties operating along the border. These threaten the sanctity of our border. Some with even ISIS connections (apparently). The Arakan Army and a bunch of others should be designated similarly and under no circumstances can they operate on Bangladeshi territory. Leave no trace of their networks and infrastructure and capture their militants for information (an area we critically lack). And if absolutely necessary, dig deep into Burmese territory.
Eliminating these threats in a coordinated manner should be the prime.
Now, the best ASEAN can do is to ensure that these do not develop into another Palestinian vs. Israeli or Kashmir like situation. These things have been there since our grandparents were kids. The world cannot afford another one.
Under no circumstances can they allow this to happen. Under no circumstances can they allow that conflict to spread. If they do, then they can say goodbye to their prosperity. And that'd be on them.
In all frankness, I doubt if they have the resolve for.....THAT.
But hey, neither are ours. Some of the most simplest solutions are the most effective.