If foreigners are caught in Lhasa, where will they be sentenced to jail?

The key depends on the location of the crime. The trial of criminal cases is generally tried by the judicial organ in the place where the crime occurred, and the sentence is generally served in the place where the crime occurred after the verdict is pronounced.

Relevant laws and regulations:

Article 24 of the Criminal Procedure Law A criminal case shall be under the jurisdiction of the people's court of the place where the crime was committed. If it is more appropriate to have the case tried by the people's court of the defendant's domicile, it may also be under the jurisdiction of the people's court of the defendant's domicile.