This report describes the installation of a high-gain, long-period seismograph system at Chiang Mai, Thailand. The station is located at 18 degrees 47 min. 24 sec. north latitude, 98 degrees 58 min. 37 sec. east longitude, at an elevation of 416 m above sea level in a concrete surface vault adjacent to the World-Wide Standardized Seismic Network (WWSSN) station CHG instrument vault. The system consists of three Geotech seismometers with natural periods of 30 sec (one vertical and two horizontal) each with two velocity transducers and one displacement transducer.