AS is usually in brackets (AS). It means ‘Peace be upon him’ in Arabic (Alayhi salam), and is said after the names of Prophets and Imams usually – for resepect.
Prophet Muhammed usually has the acronym (SAW) after his name, and this is specific to him.
The Arabic acronym is (ع) and means عليه السلام
It is shown as an image in some discussion forums like so: