He was seeking refuge. After the Second Punic War was over, Hannibal left Carthage and went to Tyre. He eventually commanded a Seleucid fleet for Antiochus III in the Roman-Syrian War.

From what I understand, he served as a military advisor and part-time commander. However, his advice did not always seem to be followed, so I have been led to believe that Antiochus' more senior (spend more time in the court) advisors and generals were jealous of Hannibal's past, creating a factionalism that undermined the Seleucid war effort.