I have never tried Similac Malaysia before. However, there are some brands that are sold in Malaysia in refill packs and they will buy it there since it is cheaper (based on rates). You may want to check on ingredients, nutrients, etc if you are cautious otherwise, you may maintain to just Singapore. Though can be expensive in price but certainly you can survey at different shops to compare prices.
I've gotten the refill packs from Malaysia. Have yet to check the ingredients list but baby's taking on to it well & no issues so far. It is a lot cheaper in Malaysia vs Singapore.