So are bicycles even allowed to cycle on the highway?
It's not a crime to cycle on highways
The Malaysian Highway Code says under Rule 66 that cyclists should avoid highways (emphasis added):-

66. Always seek and use the safest route. Keep out of heavy traffic as much as possible. Avoid highways in particular, and fast traffic in general.

The Code also mentions that as the 2nd slowest road user, cyclists need to be extra careful and one of the ways to stay safe is to avoid roads where other vehicles travel at high speeds, like highways.
This rule doesn’t make it a crime to cycle on the highway, but Section 68(3) provides that if you break the rules, it can be used against you in any court proceedings. This would also mean a driver who knocked you over could end up walking free by placing the fault on you instead.

If you were just wondering whether it's now okay for cyclists to ride out onto the highway and weave back and forth, actually they can't.
Depending on how you were riding your bike and what conditions you were riding under, you might even run into problems with the law because…

Driving laws also apply to cyclists
Section 54 of the Road Transport Act 1987 provides that laws against dangerous driving, careless driving, and even drunk driving also apply to cyclists!
Whether someone was driving "dangerously" or "carelessly" depends on the specifics of the situation, "including the nature, condition and size of the road and the amount of traffic which is or might be expected to be on the road".
For example, driving a car at 100km/h in the fast lane might be normal, but driving at the same speed on a winding road will be considered dangerous driving.

Dangerous driving (Section 42) and careless driving (Section 43) are also defined differently, which are in short:
Dangerous driving – Driving recklessly or at a speed/in a way that endangers the public
Careless driving – Driving without due care and attention, or without consideration for others on the road