Free entry can apply to a venue, a permanent display or a particular exhibition—not necessarily everything in the building. Use each venue's own visitor page to check the date, hours and admission terms before you go.
Bangkok Art and Culture Centre publishes its own visiting and exhibition information. The Bank of Thailand Learning Center also maintains official visitor information for its museum and learning spaces. These are useful first checks because the venue, not a directory, controls current access.
Check Bangkok Art and Culture Centre ↗ Check the Bank of Thailand Learning Center ↗
Look for separate terms for permanent galleries, temporary exhibitions, workshops and special events. Registration, timed entry or identity checks may still apply even when admission costs nothing. A third-party list can go out of date, so confirm on the venue's site.
The Princess Maha Chakri Sirindhorn Anthropology Centre's museum database is useful for discovering other Bangkok collections. Treat it as a directory: open the individual museum's current page before relying on its price or hours.