A one-way flight to Bangkok is easy to book. The awkward part can come before you even board: the airline asks when you're leaving Thailand, and your answer is still somewhere between probably next month and I'll decide after Chiang Mai. If that's your travel style, the important document isn't a return ticket to your home country. It's credible proof of a journey out of Thailand within the period that applies to your entry.
Thailand's rules changed in September 2026, so old articles promising the same visa-free stay to everyone are a poor planning tool. Here's how to approach the onward-ticket question without giving up a flexible itinerary.