EXHIBIT 13.1

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

         In connection with the Annual Report of ST Assembly Test Services Ltd
(the "Company") on Form 20-F for the period ending December 31, 2003, as filed
with the Securities and Exchange Commission on the date hereof (the "Report"),
the undersigned hereby certify that to the best of our knowledge:

         1.       The Report fully complies with the requirements of Section
13(a) of the Securities Exchange Act of 1934; and

         2.       The information contained in the Report fairly presents, in
all material respects, the financial condition and results of operations of the
Company.

Date: March 19, 2004                /s/ Tan Lay Koon
                                    -------------------------------------
                                    Name: Tan Lay Koon
                                    Title: President and Chief Executive Officer

Date:  March 19, 2004               /s/ Pearlyne Wang
                                    -------------------------------------
                                    Name: Pearlyne Wang
                                    Title: Acting Chief Financial Officer