Businesses starting with S
- Siam Tewa Co., Ltd.
- Siam Textile Chemical Co., Ltd.
- Siam Thai Heavy Brake (1987) Co., Ltd.
- Siam Thani Furniture Co., Ltd.
- Siam Thani Hotel
- Siam Thermo King Co., Ltd.
- Siam Timber Supply Co., Ltd.
- Siam Tin Food Product Co., Ltd.
- Siam Tinplate Co., Ltd.
- Siam Tinplate Co., Ltd.
- Siam Tokai Co., Ltd.
- Siam Toppan Packaging Co., Ltd.
- Siam Totsu Ceramics Co., Ltd.
- Siam Toyota Manufacturing Co., Ltd.
- Siam Track (luksi) Ltd., P.
- Siam Trade International Co., Ltd.
- Siam Trading Co., Ltd.
- Siam Trading Shop
- Siam Trafo Co., Ltd.
- Siam Translation Center