Is alcohol banned in Thailand, or is it the hours that confuse everybody?

Not banned. What exists is a set of retail restrictions that surprise visitors, including a block on buying alcohol outside licensed venues between midnight and 11am, with fines attached. Shops will simply refuse the sale, which people then read as a ban. Buying days around certain religious holidays are also restricted, so a supermarket refusing you is not a mistake and not something to argue about at the till. This sits with the other rules worth knowing before you arrive: https://meetlocale.com/guides/is-thailand-safe-to-travel-alone Where did the hours catch you out, and did the shop explain or just decline?