$this->db->where('group_chat','xyxy');
$this->db->order_by('waktu', 'ASC');
$get=$this->db->get('chat');
if($get->num_rows()>0){
    $data1=array();
    $data2=array();
    $no=1;
    foreach ($get->result() as $key) {
        $penentu='';
        if($no%2==1){
            $penentu='left';
        }else{
            $penentu='right';
        }

        $data1['no'.$no]=$key->chat;
        $data2['no'.$no]=$penentu;
        $no++;
    }
    $data=array(
        'text'     => $data1,
        'position' => $data2
    );
    echo json_encode($data);
}else{
}

//output
{"text":{"no1":"Tes aja","no2":"Tes juga","no3":"Hallo","no4":"Hai"},
"position":{"no1":"left","no2":"right","no3":"left","no4":"right"}}

maunya:
[
    {
        'text'     : 'Tes aja',
        'position' : 'left'
    },
    {
        'text'     : 'Tes juga',
        'position' : 'right'
    },
    {
        'text'     : 'THallo',
        'position' : 'left'
    },
    {
        'text'     : 'Hai',
        'position' : 'right'
    }
]