Report of STEC-W No.13 and STEC-W2 No.4

Ref: ST/010/2006/0026 April 3rd, 2006 Re: Report on the Exercise of Warrants (STEC-W No.13/2006, STEC-W2 No.4/2006) 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.13 and STEC-W2 No.4 on March 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: 1,882,350 shares, and STEC-W2: 163,628,461 shares - No.of STEC-W holders exercise:3, STEC-W2 holder exercise: 1 - No.of warrants being exercised of STEC-W No.13/2006: 71,600 units, and STEC-W2 No.4/2006: 80,000 unit - Ordinary shares resulted from the exercise of STEC-W No.13/2006: 71,600 shares, and STEC-W2 No.4/2006: 80,000 shares - Money received from the exercise of STEC-W No.13/2006: 71,600 Baht, and STEC-W2 No.4/2006: 680,000 Baht - 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