ขอสอบถามวิธีแก้หน่อยค่ะ ฐานข้อมูลภาษาเป็น latin1_swedish_ci ดึงข้อความภาษาไทยมาแสดงอ่านไม่ออกเลยค่ะ มีวิธีแก้ไหมค่ะ

class db_tis_2_utf{
	public $tis;
	public $utf;
	public function __construct( $host, $user, $paswd, $tis,$utf){
		$this->tis = new mysqli($host, $user, $paswd, $tis);
		$this->tis->set_charset('tis620');
		$this->utf = new mysqli($host, $user, $paswd, $utf);
		$this->utf->set_charset('utf8');
		$this->convert();
	}
	public function convert(){
		$rs=$this->tis->query('show tables');
		$tbs=$rs->fetch_all();
		foreach($tbs as $ro){ $this->transfer($ro[0]); }
	}
	private function transfer( $tb ){
		$rs=$this->tis->query('select * from '.$tb);
		$flds = $rs->fetch_fields();
		//////////
		while($ro=$rs->fetch_assoc()){
			$sql = 'insert into '.$tb.' ';
			foreach ($flds as $key=>$val) {
				$nm=$val->name; $vl=$ro[$nm];
				switch($val->type){
				case 253: case 254: case 255: // varchar
					$value = iconv('tis620', 'utf8', $vl);
					$sql .= ($key>0? "," : 'set')." $nm='$value' ";
					break;
				case 249: case 250: case 251: // blob
					$value = bin2hex($vl); $x = strlen($value)? '0x'.$value : "''";
					$sql .= ($key>0? "," : 'set')." $nm=$x ";
					break;
				default: // number, date etc.
					$sql .= ($key>0? "," : 'set')." $nm='$vl' ";
					break;
				}
			}
			$this->utf8->query($sql);
		}
		unset($rs); unset($flds);
	}	
}
$z = new db_tis_2_utf('host','user','psw','dbtis', 'dbutf');