Complaint Fingerprints of Condominium Value in Bangkok: A Within-District Test of Infrastructure Capitalization

Neighborhood quality is the hardest hedonic component to measure and is usually proxied by coarse census aggregates. I ask whether complaint composition reveals infrastructure quality that markets capitalize, or if it merely reflects unequal engagement and urbanicity. I link 556,882 geolocated complaints from Thailand’s Traffy Fondue platform (January 2025 to June 2026) to 8553 for-sale condominiums across Bangkok, geocoding each project with two independent services (76% building precision, cross-validated to 45 m), and measure the local complaint environment within 250 to 1000 m rings. Across the 45 active districts, price tracks complaint composition strongly, but the fingerprint is collinear with urban density and collapses once complaint density is controlled. The central contribution is a within-area test: conditional on district and sub-district fixed effects, condominiums in a locally more flood-prone micro-location sell for less, 4.4% per standard deviation, strengthening with radius and with geocoding precision, and surviving false-discovery-rate correction. Complaint-mix diversity is likewise capitalized. Footpath share is positively signed but does not survive correction: complaint composition is two-dimensional, some categories indexing disamenity, others urban intensity. Regional PM2.5 haze carries no within-city signal. Citizen complaints are thus a spatially resolved fingerprint of local environmental quality, capitalizable only where the signal is local.