Do I need a return ticket to board my flight to Thailand on a retirement visa?

When I have arrived on a 1 way ticket and been asked (around 3 times in total) I have just said Im not sure when I will be leaving yet and that I will make sure I will leave before the end of my exemption or visa

When they ask about accommodation I say Im booking a guest house for a couple of nights while I look around for something more long term

Everyone is guilty until proven innocent these days! Point being you havent broken any law until you overstay your 'welcome' 🤷

That said, if you are worried, book the cheapest excursion out of Thailand before your visa ends and use that as proof and simply dont use it. A £30 flight to say Vietnam would suffice

Not related to your question but how long did it take to get the visa after application date?

Just show your O visa to the airline at check in as you do not need a return or onward ticket with a long term visa

Buy a bus ticket out of Thailand its very cheap and easy to get rid

They denied me checking in from spain to bangkok without a return ticket, i booked one from bkk to singapore on the spot for 50$ just to show her i would “leave”

Just book a fully refundable flexible air ticket out of Bangkok (with minimal cancellation admin fees), or check if any airline flying out of Bangkok (eg those US airlines) which allows free cancellation within first 24 hours of booking, then make a dummy booking a few hours before u board your AMS flight to Bangkok, and cancel that dummy booking for free once u got your boarding pass to Bangkok

You’re fine. Just show them the visa.

Speak to the Thai embassy….😂

A non-immigrant visa does not require onward travel