Start by deciding which coast you actually need
Krabi (KBV) is a mainland airport for Ao Nang, Krabi Town and onward boats to places such as Railay and the Phi Phi islands. Koh Samui (USM) puts you directly on Samui and can connect onward to Koh Phangan or Koh Tao. They are not interchangeable “south Thailand” airports: choosing the wrong one can add a long road-and-ferry day.
I search Chiang Mai (CNX) to each airport for the exact date before fixing hotels. Nonstop service can be seasonal or limited to certain days, while connection choices move throughout the year. A live airline result beats any static weekly-frequency claim.
Chiang Mai to Krabi: nonstop first, Bangkok second
When a suitable nonstop is operating, Krabi is the simpler north-to-Andaman move. The airborne time is roughly two hours, but I treat hotel checkout, airport time, baggage and the Krabi transfer as most of a travel day. AirAsia's current destination search includes Chiang Mai–Krabi, though the operating days and fare shown for your date are what matter.
A connection through Bangkok can be sensible when it produces a much better fare or timing. Check the airport code carefully: BKK is Suvarnabhumi and DMK is Don Mueang. A single itinerary through one airport is very different from two tickets that require baggage collection or a transfer across Bangkok.
Krabi airport is not the beach
Landing at KBV does not mean the journey is over. Krabi Town, Ao Nang, Railay boat piers and island transfer points all require different arrangements. I book the first transfer around the flight's realistic arrival, keep the accommodation name offline and confirm the last boat or shared-transfer cut-off directly.
If the flight lands late, a mainland night can be safer than chasing an island connection. Boat schedules depend on route, season and weather; a flight delay does not oblige a ferry operator to wait.
Chiang Mai to Koh Samui: price the convenience honestly
Samui's airport saves the mainland road-and-ferry transfer. Bangkok Airways' current booking and deal pages include Chiang Mai–Samui options, but nonstop availability is date-specific and some searches may return a Bangkok connection. I compare the live itinerary rather than assuming a direct flight runs every day.
Samui fares can look high beside mainland alternatives. That premium buys arrival on the island, not simply a seat on an aircraft. Compare it with the combined price and time of flying to Surat Thani or another mainland gateway, transferring to a pier, taking the ferry and then reaching the Samui hotel.
The mainland-plus-ferry alternative
A cheaper flight to the mainland can work for flexible travellers, but it creates a chain: flight, baggage collection, road transfer, ferry check-in, crossing and island transfer. Search it as a complete itinerary. If different companies sell separate pieces, you carry the missed-connection risk unless the product explicitly protects the whole journey.
I avoid the final possible ferry after a separately booked flight. Weather, air delays and road traffic make the theoretical connection less comfortable than the timetable suggests. An overnight near the pier or on the mainland may be a smarter use of the saving.
One booking is worth more than it looks
On a protected itinerary, the carrier has defined procedures when the first flight disrupts the connection. On separate tickets, the second airline may treat you as a no-show even when the first flight was late. I identify the ticket numbers, operating carriers and baggage arrangements before paying.
Where a codeshare appears, confirm who operates each sector and which airline handles check-in. Bangkok Airways' current codeshare guidance also tells travellers to identify the operating carrier and notes that through-checked baggage depends on the applicable route and partner conditions.
Baggage can reverse the cheapest fare
Island trips often involve more luggage than a short city break. Compare the exact cabin and checked allowance, sports-equipment rules and fees. A diving bag, large backpack or family luggage can erase a low headline fare. Boats may also have their own luggage conditions, so a generous airline allowance does not settle the ferry question.
Keep medication, documents, valuables and one change of clothes in cabin baggage within the airline's limits. If a checked bag is delayed, an island transfer makes recovery more awkward.
How much connection time?
There is no universal safe number. For one ticket, follow the offered legal connection but decide whether you personally want more margin. For separate tickets, include arrival delays, disembarkation, baggage delivery, terminal movement, re-check-in and security. I would rather spend a calm extra hour than buy a new southbound ticket.
Airports of Thailand currently advises passengers at Chiang Mai airport to allow at least two hours before departure. I keep that conservative baseline even after online check-in, then add road contingency from the hotel.
Choose by itinerary, not airport price
- Ao Nang, Railay or Andaman islands: price Krabi first and protect any onward boat.
- Samui stay: compare USM convenience with the full mainland-and-ferry chain.
- Koh Phangan or Koh Tao: work backwards from a realistic ferry connection and weather margin.
- Very short holiday: pay more attention to elapsed door-to-door time than the lowest fare.
- Flexible slow trip: an overnight mainland stop can make a cheaper route comfortable.
Weather and season are operational facts
Andaman and Gulf islands do not share identical weather patterns. Heavy rain, wind and rough seas can alter boats even when aircraft operate. Check current airline status, local weather and the ferry operator close to travel, and avoid prepaid same-day activities after a complicated connection.
My north-to-south checklist
- Choose the coast and final island before searching the flight.
- Check live nonstop availability for the exact date.
- Compare total fare, baggage and complete door-to-door time.
- Reject accidental BKK–DMK changes unless deliberately planned.
- Identify separate tickets and leave a large self-transfer buffer.
- Protect the final ferry or sleep before it.
Sources checked for this guide
I checked AirAsia's live destination search, Bangkok Airways' flight-schedule tool, its current codeshare guidance and the official Chiang Mai airport guidance on 15 September 2026.
Cheers, Carpe Diem & protecting the ferry after the flight! 🍻⏳⛴️
TATS Man
your one-booking-before-two-tickets island-hop correspondent