Has anyone become an ace-trader under the tiger brokers promotion? How long do the status and benefits last? And do I meet the criteria if I trade SGX stocks?

You can become an "Ace Trader" simply by making more trades. SGX trades qualify, even though there is a no minimum commission promotion currently going on. Technically you could make multiple small SGX trades (eg. 10x HST/ES3) in order to hit the goal of 200 trades within a month.

Check out this guide on how to get Ace Trader status.

Aside from gaming the system to get the benefits, it is a scheme to encourage users to trade more and increase commission revenue. Without the no minimum commission promotion, you would need to accrue at least 400 USD (or its equivalents) in commission, which isn't really worth it.​​​