2. The rainy season begins around mid-May to mid-October. This season will begin when the southwest monsoon. The moist winds blowing over Thailand. Meanwhile, a trough of low pressure. (The ridges, causing rain) across the country, making it the wettest general. A trough of low pressure over the south usually begins in April. Then move up across central and eastern North and Northeast. In May and June, respectively. In late June, will move to areas across southern China. Rain fell in a while and called a "rainy period," which may last for about 1-2 weeks, or a few years, potentially severe and less rain for many months. Around August to November, a trough of low pressure packages. Will move back down south again across the country. It lies in order from north to south. Thailand will be made at such times, heavy rain continued. The upper Thailand will wettest months of August and September. And Southern wettest October to November. Over time, a trough of low pressure moves up and down it. Thailand will be the influence of the southwest monsoon. The covered at all times But some might term strength. Some stages may be weak Based on the location of the ridges in the low pressure. By mid-October monsoon