How to invest S$1M?

My dad is inheriting about S$1M from his (childless) sibling who passed away earlier this year. My dad does not have much financial literacy and is seeking my advice on how to place these funds for passive income and capital growth. I am keen to support given this will likely be my inheritance one day.

I do not have experience investing such a large quantum. My personal portfolio is around $200K in stocks, RSUs from income, cash, TDs, Crypto so I have some basic knowledge on retail investing.

Does anyone have experience tapping on bank premier banking relationship for access to more high yield products? We are likely to go with OCBC Premier Banking because that is where the inheritance is sitting.

Keen to hear experience and lessons from others who had 'windfall' and how they dealt with the sudden influx of cash.