This is the ideal month to explore the north around Chiang Mai and Chiang Rai as the average temperature rises to around 25°C, it’s dry and has low humidity - perfect hiking weather. A possible bonus is to coincide your visit with the Chiang Mai Flower Festival that’s usually held over the first weekend of February to celebrate the end of the 'cool season' with a parade and colourful displays of chrysanthemums and the Damask Rose.
Head south to Bangkok and the west coast beaches for blue skies and a bit more heat heading up the high 20s°C. February’s a great time to visit Khao Sok National Park to explore the rainforest as the humidity will be relatively low and you can expect only a few showers. It is a rainforest after all!