If you mean the best time to visit Malaysia weather-wise on a Baktrax tour then only one word needed; ANYTIME.
If you mean for a safe, friendly and relaxed holiday and a real cultural experience along with some of the best food on earth at a local level then again the same: Anytime is the best time to visit Malaysia.
While the East coast has some severe weather at certain times of the year the Baktrax region which is the central & west coast is not as harsh when it comes to storms. While it can rain at any time of the year and often does the wettest time is between August and November. Like all the other countries in the region, the rain usually comes in short but very heavy downpours. Twenty minutes later all gone. Another coffee or beer while you wait for the drains to clear the water at times also.
Apart from the Cameron Highlands, it is always hot to even more so at times. The temperature very rarely drops below 20C at night and usually gets to 30C daily. It is similar all year.
The Cameron highlands and the main town of Tanah Rata have cooling blanket weather all year at night due to the altitude of 1,440 metres above sea level, but rarely cold days. Some welcome relief from the heat below all year round. The rain is more likely to be a longer fine drizzle than the short heavy downpours below. The temperature range is generally between 14C & 24C all year.
In regards to those wanting the best time to visit Malaysia to avoid the high season crowds then December and January would be the last choices.
So while it may be best to avoid Cambodia, Laos, Thailand & Vietnam at certain times of the year you can visit Malaysia anytime.
If you could only ever do one overseas trip then Malaysia would be as good a choice as any other with the best time to visit Malaysia being whenever you want. You won’t be disappointed. GO NOW!