According to the information I know, there are two options for the entrance from Beijing South Railway Station to Tianjin Intercity, one is the south entrance and the other is the east entrance.

However, judging from some information, when taking a bus from Beijing South Railway Station to Tianjin, the departure gate will usually stop near the east entrance, so it may be more convenient to enter from the east entrance.

Please note that the conclusions I give are based on known information. If there is the latest information or the specific situation changes, you may need to further verify.

For transportation, especially when it comes to public transportation such as trains and subways, it is recommended to check the latest transportation guide or consult relevant agencies before traveling to obtain the most accurate information.