The upper right corner is stamped.

On the right side of the diaphragm, it says at the top: recipient, address, province, country, postal code.

Then leave a line or two blank.

Write down the address of Singapore below.

There will be a machine in Singapore and Malaysia, which I have seen in airports and urban areas. Sam (self-service automation machine) is a machine that can buy stamps and mail them. Choose a country and stamps will come out. The machine is quite powerful, and the language seems to have Chinese.

Another thing is that you can buy postcards from the airport. Or Chinatown, it will be 50 cents cheaper than paying,