There is no set answer for this question. You can visit Thailand any time of the year. However, it is most recommended to visit the country in the dry season (November to April). During this time, temperatures are cooler and the weather is almost always perfect for outdoor activities and excursions.  That being said, the dry season is when the country sees the most number of tourists. Flights and accommodation prices are also higher than usual.  If you want to avoid the crowds, you can visit Thailand between May to October during its shoulder- and rainy season. While you may have to contend with short-lived rainshowers, you’ll get much cheaper flight prices and accommodation rates.