According to the Guinness Book of World Records, Michael Jackson holds the record for the most songs that enter the Billboard Hot 100 chart, with 50 entries. However, this does not account for songs that were not released as singles or songs that were not included on the Billboard charts.
Additionally, Michael Jackson's career spanned over several decades, and he likely performed countless songs live during concerts, performances, and other events that may not be officially recorded or released. Therefore, it is challenging to provide an exact number for the total songs Michael Jackson sang in his lifetime.