Why is Malaysia a tropical rain forest with obvious dry and wet seasons?

Malaysia is rainy all year round, but the dry and wet seasons are not obvious. The rainy season is 1 1 ~ 1, and the precipitation in three months is about 750~ 1000 mm, accounting for more than one third of the whole year. The reason for the difference in monthly precipitation is that Southeast Asia is a monsoon region and Malaysia is also a monsoon region, which is alternately controlled by southwest monsoon, northeast monsoon and equatorial convergence zone. However, unlike China, Malaysian winter monsoon and summer monsoon alternate, and only the wind direction changes obviously, but the rainfall does not change much. The monthly precipitation in rainy season from 1 1 to 1 is 250~350. 1 1~ 1 Due to the influence of the northeast monsoon, it brought a lot of cold air to Southeast Asia, formed a cold wave, intensified the convective activity in Malaysia in winter, and made the thunderstorm weather stronger and stronger, resulting in a rainy season with relatively heavy rainfall.