50k USD bro, is erm, not a small amount in not-so-"maju" Malaysia.

The foreign expats surely can afford it, but not likely to be the case for all undocumented foreigners.
You should apply bro. Risk free rates are rising sharply now except when BOE messed things up yesterday...
Yes, for competitive bid, you can bid at any rate you like, minimum 1000 SGD up to 1 million SGD per competitive bid. If the auction result is such that your bid rate (e.g. my bid was 3.5%) is higher than the cut-off yield (3.32% in this recent issue), then your money will be refunded (unsuccessful application). If you bid 3.30% for example, and the cut-off yield is 3.32%, then you will be successful in the bid. If your bid rate is exactly the cut-off yield (e.g. you bid 3.32% and cut-off yield is exactly 3.32%), then you can expect partial allocation.
You need to put your funds upfront (again, 1000 SGD - 1 million SGD for competitive bid), the application opens 1 week before the auction date and closes 1 day before auction date. To earn some more bank interests, I usually apply at the last minute (around 5 pm for DBS, deadline is 9 pm the day before auction day) but there are risks associated so some people apply a few days earlier instead.
If you are successful in the bid, at around 5pm or 10 minutes past 5 the same day as auction results are announced, DBS will refund you the discounted value of the bill (i.e. your "interest") and the bill is held by MAS till maturity when the entire bill is retired at par value, i.e. (the 1000 SGD - 1 million SGD amount you bid for earlier). Of course, this is provided MAS/SG government is still functioning 6 months after the bill is issued.
If you are not successful in the bid, e.g. CDP account not yet set up, DCS service still not activated, or like in my recent case (today), my bid yield is higher than the cut-off yield, so my entire bid amount (1000 SGD) will be refunded around the same time as the case if bid is successful and discounted value is refunded, i.e. around 5 pm to 10 minutes past 5 the same day as auction results are announced.
Note that DBS is always the slowest among the 3 primary dealers in refunding unsuccessful bid/pay discounted value. OCBC and UOB usually refund unsuccessful bid/pay discounted value to you shortly after auction result, i.e. around 2-3 pm. DBS's 5 pm is the latest. So you might want to apply using OCBC/UOB accounts for T-bills if you have one.
This is how it looks like in my DBS account transaction summary:
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I applied for 1 6M T-bill 2 weeks ago on 14th of Sept (1k SGD deducted) and the auction was done on the 15th in which I was successful, so around 5:10 pm the discounted value was paid back to my account. Upon maturity next March year, the entire 1000 SGD will be paid back (if SG government is still financially sound). The most recent 1000 SGD debit yesterday refers to the 6M T-bill I applied yesterday which was not a successful bid and I am still waiting for the refund.
EDIT: Refund just came in at 5:09 pm.
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You can read red devil's first 2 posts in HWZ's SG T-bill thread. It's well explained there for you:
https://forums.hardwarezone.com.sg/threads/...-bills.6769601/Hope that helps bro, can always ask me here if you have problems with the application process.

Bro,... thank you very much for taking the time to write all these.
Appreciated it very much,...