A narrow-linewidth thermally tuned multi-channel interference (MCI) laser integrated with a semiconductor optical amplifier (SOA) and spot size converter (SSC) is demonstrated in this paper. A MCI laser integrated with SOA through chirped grating is successfully realized for the first time, which achieves a tuning range of more than 42.5 nm with side-mode suppression ratios (SMSRs) higher than 48 dB and Lorentzian linewidth below 100 kHz. InGaAlAs multiple quantum wells (MQWs) and thermal tuning are used to reduce linewidth. The integration of SSC greatly improves the coupling efficiency between the laser and a lensed fiber. The MCI laser integrated with SSC achieves more than 16 dBm output power coupled into a lensed fiber. Air layers are fabricated in the phase sections to increase the heating efficiency. The total thermal tuning power is below 20 mW across the whole tuning range.