After struggling for a several days, at last i found a solution.

If ui-autocomplete plugin is created from beforeShowForm function this is append to the dialog instead of the add/edit jqGrid form because the form doesn't exist yet, moving the plugin to afterShowForm seems to works ok.

Any way i still wondering why z-index=1000 of .ui-autocomplete didn't work.

code fixed:

var frmDefaults =