Is it ok and hassle free to cross a border (malaysia) whilst still on red numberplates?

i'd say: definitively forget it.

best is: ask your insurance, they'd have to cover an event.

There are a bunch of laws regarding red plates, which are minimally or selectively enforced, such as you are not supposed to drive at night, can not leave the changwat where they are registered, etc.

But- I'd agree with Danone. Ask your insurance company.

Not possible.

As siad above, you arent legally allowed to leave the changwat where its registered.

You will get away with leaving the changwat, but definately wont get away with leaving the country.

On top of that, you'll need a letter in English issued by your local Dept of Land Transport office, which states the number plates of the car in Roman characters.

To get this letter, you need the car's blue registration book, which you won't get till you get the while plates issued.