AIS Standardizes on Siebel eBusiness Applications.

Business Editors/Technology Writers

SAN MATEO, Calif.--(BUSINESS WIRE)--Jan. 28, 2002

Thailand's Premier Mobile Telecommunications Company

Enhances Business Efficiency, Customer Satisfaction,

and Profitability Using Siebel eCommunications

Siebel Systems, Inc. (Nasdaq:SEBL), the world's leading provider of eBusiness applications software, today announced that Advanced Info Service Plc. (AIS), Thailand's premier mobile telecommunications company, has standardized on Siebel eBusiness Applications. The company is using Siebel eCommunications--a version of Siebel eBusiness Applications specifically designed for the unique needs of the communications industry--to streamline its call center and sales processes. Using the rich, tailored functionality of Siebel eCommunications, AIS is replacing decentralized databases and manual systems, uniting customer information, and making it accessible across multiple sales and service channels. This approach will enable the company to improve customer service and create long-term, profitable customer relationships.

Prior to selecting Siebel eCommunications, AIS' customer sales and marketing operations relied on disparate manual systems and databases, which significantly reduced information sharing between departments. AIS recognized the need to automate its call center and sales operations and standardize sales and service processes, while extending services to new channels.

To improve customer service and create long-term, profitable customer relationships, approximately 7,000 AIS sales, marketing, and service professionals will now use Siebel eCommunications to execute an integrated, multichannel customer strategy across all departments and channels--including the call center, corporate sales team, marketing outlets, retail stores, and dealers. AIS will use Siebel eCommunications eChannel to improve the interaction between AIS and its dealer network, and is deploying Siebel eCommunications Call Center to enhance sales and service productivity and increase customer responsiveness.

"The mobile communications market in Thailand is undergoing tremendous growth, which is attracting increased competition," says Mr. Somprasong Boonyachai, President and CEO, AIS. "We chose Siebel eCommunications to improve our customer knowledge and better serve market needs. Siebel eCommunications enables AIS to significantly improve productivity and profitability and assists us in managing the challenges we face, both today and tomorrow."

About Advanced Info Service (AIS)

Considered the most potential service provider in Thailand's mobile phone business, Advanced Info Service Plc. or AIS is the mobile phone operator in Cellular 900, GSM Advance and Prepaid One-2-Call with more than 5 million registered users (as of January 2002). The key strategies implemented by AIS consist of 4 major areas including Network Excellence, Technology Excellence, Service Excellence and People Excellence, all of which play a crucial role in providing service. AIS believes that "Only truly excellent quality service creates highest satisfaction to our service users."

About Siebel Systems

Siebel Systems, Inc. (Nasdaq:SEBL) is the world's leading provider of eBusiness applications software. Siebel Systems provides an integrated family of eBusiness applications software, enabling multichannel sales, marketing, and customer service systems to be deployed over the Web, call centers, field, reseller channels, retail, and dealer networks. Siebel Systems' sales and service facilities are located in more than 37 countries. For more information, please visit Siebel Systems' Web site at www.siebel.com.

Except for the historical information contained herein, this press release contains forward-looking statements that involve risk or uncertainties. Future operating results of Siebel Systems may differ from the results discussed or forecasted in the forward-looking statements due to factors that include, but are not limited to, risks associated with customer relations, such as the availability of Siebel Systems' products and services, customer implementation of products and services, relationships with customers, third-party vendors and systems integrators, concentration of revenues in a relatively small number of customers, existence of errors or defects in products, ability to successfully manage growth, significant current and expected additional competition and the need to continue to expand product distribution and services offerings. Further information on potential factors that could affect the financial results of Siebel Systems are included in Siebel Systems' Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and its other filings with the Securities and Exchange Commission, which are available at www.sec.gov. Siebel Systems assumes no obligation to update the information in this press release.

Note to Editors: Siebel is a trademark of Siebel Systems, Inc. and may be registered in certain jurisdictions. All other product and company names mentioned are the property of their respective owners and are mentioned for identification purposes only.