Report on the exercise STEC-W and STEC-W2

Ref: ST/010/2005/0004 January 6th, 2006 Re: Report on the Exercise of Warrants (STEC-W No.12/2005, STEC-W2 No.3/2005) 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.12 and STEC-W2 No.3 on December 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: 1,888,950 shares, and STEC-W2: 163,628,461 shares - No. of STEC-W holders exercise: 1 , STEC-W2 holders exercise: 0 - No. of warrants being exercised at No.12/2005: 6,600 units, and No.3/2005: 0 unit - Ordinary shares resulted from the exercise at No.12/2005: 6,600 shares, and No.3/2005: 0 share - Money received from the exercise at No.12/2005: 6,600 Baht, and No.3/2005: 0 Baht - Total remaining warrants listed in the Stock Exchange of Thailand No.12/2005: 1,882,350 units, and No. 3/2005: 163,628,461 units Please be informed accordingly. Yours sincerely, Mr. Woraphant Chontong SEVP. Financial and Administration Division