Governments around the world have crafted new laws to threaten, arrest, prosecute and incarcerate online political activists. While the primary effect of online repression is to silence criticism and forestall collective action, a secondary effect is to induce self-censorship among the masses. Yet scant research examines how self-censorship works, nor discusses its implications for entrenching authoritarianism and encouraging democratic backsliding. This article proposes a simple expected utility model of self-censorship, arguing that citizens will more likely self-censor when the expected costs of online political expression outweigh its benefits. Analysing the fourth wave of the Asian Barometer survey of 10,216 respondents across eight Southeast Asian countries, I find that higher income politically engaged social media users are indeed less likely to express their political opinions. Additionally, this correlation holds in states where online repression is most severe, but is non-existent in countries where online repression is moderate or low.