I'm an expat in Singapore an S-Pass holder. How can I start investing in Singapore Stock Market?

You will need to open an account with a broker (like DBS Vickers or Saxo or others), and you will need to take a SGX test, to make sure you understand all the products and especially all the risks involved. Lots of paperwork to read and sign, especially to trade US, and you will also need to open a SGX/CDP account linked to your broker to keep all your Singapore stocks. With DBS Vickers, you can have a giro to your DBS bank account (if you have one) so your dividends and sell proceeds can be automatically transfered to your bank account.

Note: avoid joint accounts with DBS vickers as they limit what you can do on-line and force you to telephone instead, especially for foreign transfer. Good luck!