When to go
The best time to visit most of Thailand is between November and February, because it rains the least and it is not too hot. This period is also Thailand’s main season for festivals, like Loi Krathong.
If you plan to focus on the northern provinces, the hot season (March to May) and early rainy season (June to July) are not bad either, as temperatures are moderate at higher elevations. Northeastern and central Thailand, on the other hand, are best avoided from March to May, when temperatures may climb over 40°C. Because temperatures are more even year-round in the south (because it’s closer to the equator), the beaches and islands of southern Thailand are a good choice for respite when the rest of Thailand is miserably hot.
Thailand’s peak tourist season runs from November to late March, with secondary peaks in July and August. If you want to avoid crowds and take advantage of discounted room rates, consider travelling during the least crowded months (typically April to June, September and October).
Although the rainy season (roughly July to October) gets a bad reputation, there are some bonuses: temperatures tend to be cooler, tourists are fewer and the landscape is lush and green. Depending on the region and the month, the rains might be hour-long downpours in the afternoon. October, however, tends to be the wettest month.