In Southeast Asia, governments have increasingly tried to regulate international flows of commodities for financial, territorial, and security reasons. This article examines the relationship between borders and contraband in this arena, arguing that their interrelationship has become an important -- and understudied -- part of the regional security mosaic. The article analyses some of the connecting mechanisms between A SEAN frontier regions, and then explores how these mechanisms are being undermined by a range of countervailing forces. Here, the focus is on two contraband lines in particular: the transit of wildlife, and the passage of a diverse spectrum of consumer goods. The widening transit of such commodities presents special challenges to regional security, which are likely to plague local regimes in the foreseeable future. Introduction The security agenda in Southeast Asia has undergone significant broadening in recent decades. Arms races, the desired role of Japan, and conflict in the South China Sea have been joined of Late by cyber warfare, theatre missile defence, and dialogues on Myanmar, among other pressing issues. Scholars have looked at ASEAN's particular dynamics as a security grouping, and have even begun asking whether its characteristics and mechanics might be emulated in other parts of the world. [1] Some of these reappraisals have been part and parcel of a larger shift in the cadence of security studies, not just in Southeast Asia, but on the international stage as well. [2] Yet, there is a growing sense in the literature that Southeast Asia's security equation is especially complex, as states in this region evince highly-complicated interrelationships, governed by a broad spectrum of thorny issues. This has been true at least since the 1960s, but the swirling of these forces seems only to have gathered momentum in the last t wo decades. This article suggests that two concepts -- border permeability and illegal trade -- should have a higher profile within this widening security agenda. The examination of international frontiers in the global political economy has become a fertile field of study in recent years. Ironically, this has happened at the same time that borders are becoming less important, in terms of their restrictive capabilities. [3] Scholars have approached frontiers as part of a regional security context in various ways. Some of the best work have been done in a comparative vein, while the observations and methodologies of anthropologists on the ground have also been very instructive. [4] The transit of illegal trade through borders has also received increasing attention of late, as theorists and planners alike seek to explain how porous boundaries affect the relationships between neighbouring states. [5] Southeast Asia, with its ten sovereign nations, differing systems of government, and myriad border populations, presents an interesting case-study for these dynamics. More than most global arenas, frontiers and illicit commerce here play a fundamental part in the region's security calculus. This article examines these boundaries and flows on a systemic, pan-regional basis. An initial attempt is made to situate Southeast Asia's frontiers in a regional context, as border agreements, surveillance, and organized crime are related to government security concerns. The remainder of the article then delves into two particular contraband lines as windows into these dynamics: the trade in natural resources or biota (including flora and fauna), and the illicit commerce in consumer goods. Both are shown to be enterprises on a huge scale, which have interpenetrated the normal economic flows of the region in a wide variety of ways. The importance of these shadow circuits on commodities cannot be overstated. Money to national treasuries is lost, and ends up in the pockets of actors whose aims are often inimical to the state. Alternative power sources are built, and are then padded with this income for the future. …