Thailand April questions

Hi! I am in the process of planning and almost about to book a 13 night trip in Thailand in mid April next year. The itinerary is 2 nights in Bangkok 3 nights in chiang Mai 3 nights in Koh Samui 4 nights in Phuket

Some of the exact durations are tbc but I had a couple of questions and happy to hear some feedback! We wanted a mixture of night life, food, markets, beaches/chill out time.

The question I had specifically was based on the weather in April. Could we expect very high temperatures? Not sure about rain but any feedback would be massively appreciated!!