Can I apply for a Thai retiree visa while traveling abroad or while in Thailand as a tourist?

You never may use the e-gates when you are entering on visa, or your visa status will be changed to visa exempt and you will have a bit trouble changing your status again by directly going to an Immigration officer. (the little screen of the e-gate even ask a confirmation if you are on exempt) Using the e-gates also can be done only if you already entered Thailand ones using the manual office and that you come with the same passport

Ronny Liekens thank you. But I won’t be able to use the e- gates ? I can use the e-gates without any visa (except the 30 days when you arrive)

@Ryu *********

the easiest is the US since you can apply up to 3 months early. I would apply 2 months early at least. But you need to be traveling directly from the US to Thailand. Otherwise Laos is the fastest at about 2-3 days, but the issue there is you must apply online, get a QR code that must print, and then take that QR code to the embassy during the morning to pay in person in Thai baht.

If you do it in Vietnam it takes longer, 7 days or so, but you can do it all online including the payment. So it really depends on your priority. I find Laos boring but you wouldn't need to be there for long.