Using a historical institutionalist approach, this article addresses the future of Southeast Asia’s naval forces. Much analysis on this subject employs a linear Realist model in which Southeast Asia’s navies are expected to be the beneficiaries of declining internal security challenges and a deteriorating external threat environment. However, to date neither of these factors, including increasing Chinese assertiveness in the maritime domain, appear to have significantly accelerated naval force development in Southeast Asia. While there have been some capability increases in areas such as submarines, growth has mainly been in patrol boat and fast attack craft classes. Numbers of larger offshore surface combatants like frigates have fallen. This article argues that in countries where army dominance has become institutionalized, and civil control of the military is weak, governments may be unwilling or unable to reallocate funding away from armies to maritime forces. In a funding environment in which national economic growth is moderate, and spending on defence is a lower priority, naval modernization and expansion can be blocked. This article examines the cases of Thailand, Indonesia and Myanmar to demonstrate how their armies became dominant and how this may have diminished the growth prospects of their navies.