There are many things in Thailand that don’t make any sense to me and this is one of them.
For whatever reasons, supermarkets cannot sell alcohol throughout the day. This is also true of some restaurants and particularly restaurants located near large shopping malls. However, bars or pubs and many other independently-owned restaurants are okay to sell alcohol throughout the day.
Just watch out for this if you want to buy your favorite alcoholic beverages at a supermarket. You might be disappointed when you go during certain hours.
Please note: No alcohol can be sold during the Buddhist holiday (Thai Festivals & Holidays)
Also, you can buy alcohol inside just about any 7/11 stores, except the ones located next to a gas station. 7/11 and any other convenience stores next to a gas station are not allowed to carry alcohol. The Thai authority do not want drivers stopping to fill up with gas to have easy access to alcohol.
Here are the hours when you are allowed to buy alcohol. This is the law of the land here in Thailand: Everyday 11am – 2pm, 5pm – 12 midnight
You cannot buy alcohol in some supermarkets or restaurants between 2pm and 5pm and from 12 midnight to 11 in the morning.