Please use
select: function (e, i) {
$("#<%=hfCustomerId.ClientID %>").val(i.item.value);
},
This should work, else take a look at the fiddle below.
Fiddle for your Question[
^]
Please check the above fiddle, in which I have populated two textboxes on select of autocomplete value.
One text box with the selected value
and other static string.
Hope this helps
:)