Start from the dataset record
The catalog entry should explain the publisher, fields, format and geographic scope. Keep that metadata with a downloaded file so column names and administrative areas are not detached from their meaning.
Bangkok Open Data
Bangkok Open Data is the city's catalog for local datasets and urban-service information. Search the portal by subject, then open the individual dataset record to identify its responsible agency, coverage, update date and available files or services.
Freshness varies by publisher
The portal is a catalog, not one synchronized database. Check the resource's own update date and whether it is a current operational feed, a periodic release or a historical table.
City scope is not national scope
Bangkok Metropolitan Administration data may cover districts, roads, services or facilities inside Bangkok. Do not extend those records to neighbouring provinces or all of Thailand without another source.