Can I not buy it out of season?
It is listed as Listed season Apr–Jun. The season can differ by growing area and variety. The calendar does not guarantee that the fruit is on sale on any given day.
Lychee · ลิ้นจี่
If you want a fragrant, juicy fruit, try lychee. Peel the red rind and white flesh comes out, and one bite gives sweet taste and aroma together. If you have had it in a drink or a dessert, you could also taste the fresh fruit in season.

Listed season Apr–Jun
The season differs by growing area and variety
Kom lychee of Samut Songkhram: season listed as Apr–May
Use the main season, or the season of a regional fruit, as a guide. Actual availability can vary with growing area, variety and weather.
The white flesh is sweet, and depending on the variety you can also feel some sourness. You peel the rind and take out the stone in the middle.
Thai lychee varieties such as Hong Huay and Chakkaphat are well known. Kom lychee of Samut Songkhram is also introduced as a regional GI fruit, which makes it good for comparing fruit by growing area.
It is listed as Listed season Apr–Jun. The season can differ by growing area and variety. The calendar does not guarantee that the fruit is on sale on any given day.
Separate the units when whole fruit is sold by the kg and when it is sold in fixed packs. The season for lychee drinks on a menu and the sale of fresh fruit may not be the same.
If you want to read more about these dishes and regions, these sources are a good place to start. Ingredients and cooking methods can differ from one eatery to another.
Sharing image credit: B.navez · CC BY-SA 3.0