Wording matters,it should read like this:

"I am entering Thailand on a 90-days single entry Non-Imm-O Retirement Visa, I shall get stamped in for a 90-days stay permit.

And will hopefully be converting this 90-days stay permit to a 1-year Extension of the Stay Permit based on being over 50/Retired "

NOTE: you do not convert to any “retirement visa”. The visa becomes invalid and “used” upon entering Thailand. Sadly Thai Immigration does not draw a difference between a stay permit and a visa. For them, in their inaccurate English, it is the same thing

And regarding your question: On a 90-days single entry Non-Imm-O Retirement Visa, you won’t be asked for proof of onward travel or a return ticket, by the airline.

If the check-in crew at the airport starts asking for this, demand to speak to the manager. As this Non-Imm visa-class is meant to get converted to a long term stay in Thailand, so there is no return ticket needed

@Graham *****

he said he is applying in the UK. Maybe the upload of the colour copy had a larger file size than 3 MB. He should check his spam folder, maybe the London embassy sent an email asking for a renewed upload . . .

@Lynnette ******

😎 🤓 🙂 finish the sentence, please. " . . . . you get a 90-days stay permit" . . . . . the "permit" wording is essential, as only "90 days stay" might leave the impression you got stamped in "for" a 90-days visa. A visa is not a stay permit. . . I am trying hard not to be pedantic, but with a little passion you can sound like a real expert

@Jim ******

😂 😂 the more documents you shovel across the counter, and your Thai wife interferring, the more confused the bank staff becomes, and will pull out of their noses a requirement you have never heard or read about before! . . . .The ONLY stuff you need is: a Thai phone number, a certificate of residence from Immigration that says it is for opening a bank account, your passport and your long-term Non-Imm visa type document . . . .

@ยุถิกา *************

those were the entry stamps and/or extension stamps. These are Immigration's own stamps and can be transferred. They won't touch visa stickers or .pdf visa documents. And entry stamps ALWAYS contain the "visaclass" that was used, in the right upper corner

@ยุถิกา *************

they don't have any "visa". And even IF they had one, Immigration does NOT transfer any visas, as it is not one of their stamps

Thai Immigration won't give you any issues. They only start to ask if they are looking for a way to deny entry. . . . It is the airline that CAN ask for a proof of onward travel within the 60 days you will get stamped in visa-exempt. Some airlines accept if a return ticket is within 90 days. However most airlines only acknowledge a "real" flight ticket out of Thailand within the 60 days

keep in mind that a multiple re-entry permit (you dont buy a "multiple entry visa"!) for 3800 Baht only keeps the initial 90-days "admitted stay" permit valid. You do not gain any extra days on top of the 90 days you get stamped in on first entry

@Rich ****

absolutely worth while, but only if one of the few experts of the visa advice groups is catching up on the question. Sadly, the majority of the comments are stupid or wrong advice

@Sean *****

many ChatGPT advices regarding Thailand are wrong. Because ChatGPT sources a lot of wrong info out of the many Facebook groups, where everybody and his grandmother feel free to spread wrong info