Information of the 12th Exeercise of STEC-W No.12/2005

ST. 010/2005/0090 December 19th, 2005 Subject: Information of the 12th Exercise of STEC-W (December 2005) Attn: President, Stock Exchange of Thailand (SET) Whereas, Sino-Thai Engineering and Construction Public Company Limited, had its report on the Exercise of STEC-W that had to exercise every quarters. The total report on the Exercise of STEC-W was 11 times and the latest number of warrants being exercised on the Exercise of Warrants No.11/2005 on September 30th, 2005 is 299,700 units and it is therefore the total remaining warrants listed in The Stock Exchange of Thailand is 1,888,950 units. We would like to inform the information of the 12th exercise of STEC-W as follows: 1. The notification period of the exercise of STEC-W is during December 21st - 29th, 2005 at 8.30 a.m.- 3.30 p.m. 2. The exercise date will be on December 30th, 2005 3. Exercise ratio: 1 warrant for 1 common share Exercise price: Baht 1.00 per share 4. Documents to be submitted: 4.1 Letter of intent to exercise the warrant (the letter of intent can be picked up at the company's office). 4.2 Warrant certificate which has been signed as transferor by the owner or the SET Substitution Form (in case of warrant certificate is lost). 4.3 Pay the amount by check or cashier check, which can be cashed in Bangkok within 2 business days after exercise date. Make check payable to "Sino-Thai Engineering & Construction Public Company Limited". 4.4 For Natural Person: Copy of Identification Card / Copy of Passport which has been certified. For Juristic Person: Copy of Company Certificate which has been certified. 5. Contact Place: Sino-Thai Engineering & Construction Public Company Limited 32/59-60, Sino-Thai Tower 25th Fl., Sukhumvit Soi 21 Asoke Rd., Klongtoey Nua, Wattana, Bangkok 10110 (Ms. Krittima Sukanich Sino-Thai Tower 25th Floor) Tel: 0-2260-1321 Ext.305, 212 Fax: 0-2259-4427 E-mail: ir@stecon.co.th 6. Other Conditions: 6.1 The exercise ratio is 1 warrant to 1 share of the Company according to the adjustment of exercise price and exercise ratio under clause 1.15 of the prospectus, and the resolutions of the Board of Directors' Meeting No. 2/2003 dated on June 19, 2003. 6.2 Where the Company does not obtain the rights warrant certificates or the replacement of rights warrant certificates in full as specified in the exercise notice and/or the Company finds that the exercise notice has been inaccurately or incompletely filled in by the holder of those certificates and/or has inadequate stamps and duties as required by relevant laws and regulations, the certificate holder shall rectify the found error. If the certificate holder fail to correct within the specified period, the Company shall deem that the notification of intention to exercise expire without any exercise and shall return the previously received payment with no interest reimbursement and the certificates to the holder by registered mail within 14 days from the day succeeding the exercise date. 6.3 When the certificate holder who wishes to exercise his/her rights has fully complied with all conditions governing the notification of intention to exercise - i.e. the certificate holder has delivered the rights warrant certificates or the replacement of rights warrant certificates and the exercise notice and payment in full, the exercise cannot be withdrawn. 6.4 When the last exercise date expires but the certificate holder has not completely complied with all conditions governing the exercise, the warrant certificates and the replacement of warrant certificates shall be deemed to expire without exercise and the certificate holder cannot exercise his/her rights again. 6.5 Please find other necessary conditions, in the prospectus Part 3. Please be informed as stated. Yours sincerely, Mr. Woraphant Chontong SEVP.- Financial and Administration Division