The Southern Baptist denomination doesn't hold any particular stance regarding the gift of speaking in tongues.
If you took a survey of all the different Southern Baptist churches, you would come up with a variety of beliefs on the subject.
From their FAQ regarding speaking in tongues:
Probably most believe that the "gift of tongues" as described in the Bible ceased upon the completion of the Bible. Some may view speaking in tongues as a spiritual gift given to some Christians enabling them to communicate the Gospel to foreign cultures in a language the speaker had not known previously. A very small minority might accept what is commonly practiced today in charismatic churches as valid.
There has been some debate among Southern Baptists regarding speaking in tongues, with varying views mentioned above.