Report on the Exercise of STEC-W No.14 and STEC-W2 No.5

Ref: ST/010/2006/0045 July 4th, 2006 Re: Report on the Exercise of Warrants (STEC-W No.14/2006, STEC-W2 No.5/2006) 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.14 and STEC-W2 No.5 on June 30th, 2006 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: 1,810,750 shares, and STEC-W2: 163,548,461 shares - None of both STEC-W and STEC-W2 holders exercise the warrants. - Total remaining warrants listed in the Stock Exchange of Thailand of STEC-W:1,810,750 units, and STEC-W2: 163,548,461 units Please be informed accordingly. Yours sincerely, Mr. Woraphant Chontong SEVP. Financial and Administration Division