That is a tricky question considering the current issues of the model for an ASEAN currency, the Euro.
The main benefit of the Euro is that it prevents competitive devaluations from member countries, limiting artificial perturbations of the single European market. Trade is therefore greatly enabled between the Eurozone countries as money can move freely, and the currency is “transparent”: no change fees, no transfer fees, no monetary distorsions.
The main disadvantage is for countries with “weaker” economies (such as Greece) that have to cope with a strong currency (pulled up by the strong economies like Germany) and therefore cannot price down their productions. They cannot boost their competitiveness through currency devaluation.
It is therefore unlikely that a single ASEAN currency would be implemented before the disadvantages for the weaker economies outweigh the trade benefits of a single market with a single currency.