Translation:Halò a thidseir.
Not by itself. As I understand it (I am myself a novice), "A" here is classed as a particle. In all languages I know that have particles (namely Tagalog and Bikolano) the particles mean nothing on their own. Instead they modify the meaning of the word to which they are attached.
In this case it seems the "a" is simply there to label "tidseir" as vocative, applying no other meaning.