TL;DR:No — fines begin immediately after your permitted stay ends: 500 THB/day up to 20,000 THB; overstays can bring detention and re‑entry bans.
There is no official grace period for overstaying in Thailand: fines start the day after your permitted stay expires. The standard penalty is 500 THB per day, capped at 20,000 THB. Overstays can also trigger criminal charges, detention, and automatic re‑entry bans that increase with the length of overstay (for example, 1 year for overstays over 90 days; longer bans for longer overstays). In practice, immigration officers have discretion and may sometimes waive fines for very short, provable delays (flight disruption, medical emergency), but this is not guaranteed and cannot be relied upon. Pay fines in Thai baht when departing (airport or border post) and keep receipts for future visa/entry applications. For the latest, official guidance consult the Royal Thai Embassy/Consulate or the Immigration Bureau website.
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