Tldr: The brochure promised 5% to 9% return on investment but instead it was negative 5% for me, so you pandai-pandai la gamble your money.

I'm currently on an investment link plan by one of the big ones.
As far as I understand:
The amount of money I pay in premiums buy a certain number of unit trust managed by the insurance company.
The number of units I get depends on the current price of that trust.
The insurance company will then minus from these units the cost of my medical card, management fees and sales commissions.
The amount they minus will change based on the cost of your medical insurance etc.

The amount they charge you is fixed in RM, whereas the amount of money in your account depends on the price of the unit trust.

From the very start, they charge you the full amount. So even if your unit trust fail completely, every year you are paying enough to keep you covered. But you will be losing alot of money for nothing.

If your unit trust does very well, then there is a chance you can still have coverage for few years even if you don't pay even one sen. Depends how many unit trust in your account and the price of each in RM.

For me, the unit trust that I bought with this insurance hasn't been doing well. In the brochure they promise me 5-9%, whereas this one was negative 5. So I'm going for standalone medical instead and I invest in something that gives guaranteed returns, like a regular bank.