 This paper uses GNSS stations observational data, global ionospheric maps, and the electron density of Formasat-7-Cosmic-2 occultation to study ionospheric anomalies before the Hunga Tonga Hunga Hapai submarine volcanic eruption on January 15, 2022. The study finds negative total electron content, T.C., anomalies by three GNSS stations on January 5, with a maximum outlier exceeding 6-Techu near the epicenter of the eruption. The equatorial ionization anomaly, EIA, peaks shift significantly towards the Antarctic from afternoon to night and disappears on January 7. A maximum value exceeding NMF-2 at an altitude of 100,130 km above the volcanic eruption is found on January 5, with an electron density of 7.5x105L-CM3. This article was authored by Jindy Fong, Yun Bin Yuan, Ting Zhang, and others. We are article.tv, links in the description below.