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Special savings account - recently, we have seen a rise in these kinds of accounts(OCBC 360, DBS multiplier, SCB Bonussaver, CIMB starsaver). They are basically accounts that can unlock a higher interest once you fulfill certain requirements(credit card spending, salary crediting, monthly savings increment etc). The yields are higher than most fix deposit and you can transfer your cash out anytime, which makes it a no brainer if you can comfortably meet the requirements. Interest enters on a per month basis so it enables compounding if you have not hit the cap.
Running ads on your blog - this is not really counted as a capital guaranteed income, because you dont need any capital for it, just time and interest. But the fact that it doesn't require capital, makes it even safer dont you think? Create a blog, write on things that you are passionate about, drive in traffic and monetize. Quite a simple concept, but quite a challenge to sustain if you are writing for the sake of it. So I suggest to treat this as a hobby that you enjoy doing.
Investment grade bonds - the minimum amount of 250k might be too much for some, but sgx is currently reviewing their practices to break up the lot size to a smaller board lot size of 1000. Not only that, but this option will only be given to issuers with credit rating of 'BBB', $1 billion market value and with min issue size if $300mil. So we may get quality small lot bonds in the future. Although bond prices fluctuate with interest rate, the issuer are obliged to pay back the full principal at par on maturity. The accrued interest which enters daily into the bond value(unlike stocks) also makes it much less volatile.
Do feel free to share if you know of anymore 'pockets of income'.