Will my check-out date be considered the 30th or 31st if my flight leaves at 2 AM on January 30th?

If you arrive at the airport late on January 29th for a flight that departs at 2 AM on January 30th, Thai immigration typically views your departure as occurring on January 30th. Most international airports don't penalize for a one-day overstay if your flight is in the early hours.