This is a common question for divers. The basic rule is that the recommendations can vary, but here's the current guidance from PADI and DAN:

• Single dives – A minimum pre-flight surface interval of 12 hours.

• Repetitive dives or multiple days of diving – A minimum pre-flight surface interval of 18 hours.

For most dive trips, such as liveaboards that include multiple dives each day, the recommendation is 18 hours. For example, on a typical 4-day liveaboard to the Similan Islands, the last dive is usually before lunch on the final day, and you’ll be back on land by the evening. This allows you to fly safely the next morning. Some people prefer to wait 24 hours, and if your schedule allows, it’s a good idea to take a full day to relax before flying. Be sure to check the itinerary for your trip to know when the last dive will be and plan your flight accordingly.

Important Note: These recommendations help reduce the risk of Decompression Sickness (DCS), but they don't guarantee complete protection. Dehydration, especially in hot climates like Thailand, is a major factor. Be sure to stay well-hydrated during your dive trip.