You can't choose which ETFs to buy in SA. Only can mess with risk index,which different risk index holds different (etf) funds.

There's no risk index that has ARKK, not in SA.

closest way I know people do is buy via FSM MY / SG / HK feeder funds, or buy the ARKK via NYSE directly from foreign brokers like tradestation global (IBKR), Tiger Brokers, or TD Ameritrade. But due to currency conversions etc and fees involved in "moving" funds it may not be cost effective if the amount is too small.