Can I only buy it in season?
It is listed as Harvest listed Apr–Jun. The harvest period can vary by growing region and variety. The calendar does not guarantee that it is on sale on any given day.
Lychee · ลิ้นจี่
If you want fragrant, juicy fruit, try lychee. Peel the red rind and you find white flesh, and one bite gives you sweetness and aroma together. If you have had it in a drink or a dessert, try the fresh fruit in season too.

Harvest listed Apr–Jun
Timing varies by growing region and variety
Samut Songkhram Kom lychee: harvest listed for Apr–May
Use the main harvest period, or the harvest window for a regional fruit, as a guide. Actual availability can change with growing region, variety and weather.
The white flesh is sweet, and some varieties have a tart note. Peel the rind and eat the flesh, removing the seed in the middle.
Thai lychee varieties such as Hong Huai and Chakkraphat are well known. Kom lychee of Samut Songkhram is also introduced as a regional GI fruit, so it is a good fruit for comparing growing regions.
It is listed as Harvest listed Apr–Jun. The harvest period can vary by growing region and variety. The calendar does not guarantee that it is on sale on any given day.
Separate the unit when whole fruit is sold by the kilogram from when it is sold in a fixed pack. The harvest period for fresh fruit may differ from when lychee drinks are on the menu.
If you want to read more about the food and the regions behind it, these sources are a good place to start. Ingredients and recipes can vary from one restaurant to the next.
Sharing image credit: B.navez · CC BY-SA 3.0