Thailand experiences its longest day of the year on June 21 as the summer solstice occurs, with Bangkok seeing about 12 hours and 56 minutes of daylight. The event is caused by Earth’s axial tilt, not its distance from the sun, and coincides with monsoon conditions across the country.

NARIT says the full moon on Sunday (May 31, 2026) will be slightly smaller than usual as both the year’s farthest and the month’s second full moon.