April in Thai is เมษายน pronounced may-săa-yon. Like all months (เดือน deuan) in Thai that have 30 days, it ends with ยน (yon.).
The abbreviated version of เมษายน is เม.ย.
The beginning of เมษายน is เมษ (mâyt) coming from the Aries zodiac sign. The reason for this is that months in Thai all come from zodiac signs.
By far the most popular festivity in April is Songkran สงกรานต์. Songkran is the Thai new year and it is celebrated on April 13. But the celebration goes on for a few more days.
Songkran is also known as the water festival เทศกาลน้ำ (tâyt-sà-gaan náam) because during Songkran a lot of people in the streets will be using water guns and buckets to splash water at each other.
I hope you learned how to say April in Thai เมษายน may-săa-yon and also learned about holidays during April.