Report on the Exercise of STEC-W,STEC-W2

Ref: ST/010/2005/0069 July 4th, 2005 Re: Report on the Exercise of Warrants (STEC-W No.10/2005, STEC-W2 No.1/2005) To: The President The Stock Exchange of Thailand Sino-Thai Engineering & Construction Public Company Limited would like to report the exercise of STEC-W No.10 and STEC-W2 No.1 on June 30th, 2005 as per following details: - Exercising ratio: 1 unit of warrant per 1 ordinary share - Exercising price of STEC-W: Baht 1 per share - Exercising price of STEC-W2: Baht 8.50 per share - Ordinary shares reserved to support the exercise of STEC-W: 2,278,850 shares, and STEC-W2 : 170,000,000 shares - No. of STEC-W holders exercise: 3 , STEC-W2 holders exercise : 17 - No. of warrants being exercised at No.10/2005: 90,200 units , and No.1/2005: 5,364,607 units - Ordinary shares resulted from the exercise at No.10/2005: 90,200 shares, and No.1/2005 : 5,364,607 shares - Money received from the exercise at No.10/2005: 90,200 Baht, and No.1/2005: 45,599,159.50 Baht - Total remaining warrants listed in the Stock Exchange of Thailand No.10/2005:2,188,650 units, and No.1/2005: 164,635,393 units Please be informed accordingly. Yours sincerely, Ms. Anilrat Nitisaroj Vice President - Investor Relations