The chiral C symmetric molecule 1,2-dithiine (1,2-dithia-3,5-hexadiene, CHS) has been identified as a possible candidate for measuring the parity violating energy difference between enantiomers. We report here the observation and analysis of the low-frequency fundamental ν using highest resolution synchrotron-based interferometric Fourier transform infrared (FTIR) spectroscopy in the terahertz range with a band center of ν = 6.95375559 THz (ν̃ = 231.952319 (10) cm) and two related hot bands, the (ν + ν) ← ν band at ν = 6.97256882 THz (ν̃ = 232.579861 (33) cm) and the 2ν ← ν band at ν = 7.01400434 THz (ν̃ = 233.962001 (14) cm). This success in the difficult analyses of the THz spectrum of a complex chiral molecule of importance for fundamental tests on molecular parity violation is enabled by the ideal setup of an FTIR experiment of currently unique resolution with the very stable and bright synchrotron radiation at the Swiss Light Source (SLS).