The Bible makes a clear distinction between the Baptism of the Holy Spirit and the Filling of the Holy Spirit. They are not the same. In direct reference to your question, some believe that the Bible teaches that speaking in tongues is the manifestation that occurs when a person receives Christ. They also teach that speaking in tongues is the sign of being baptized and filled with the Holy Spirit.
When Peter preached to Cornelius in Acts 10, Cornelius and his family received Christ before Peter’s sermon was even finished! They simultaneously spoke in tongues. Peter took this as a sign that even Gentiles could receive Christ. He thought previously that only Jews were welcomed into the family of God.