You can try an immigration office but you'll probably have to go back to wherever you got the stamp to get it corrected

@Jack *******

try reading what I said. Nothing there conflicts with doing it earlier, just that you need to have that time remaining, if you have less they won't allow the conversion

@Jack *******

that's for an extension. He asked about conversion

To convert a tourist entry to a Non-O visa you need to have between 15 and 21 days remaining on your current stamp and have the required funds in a Thai bank account. If you don't have a bank account it's almost impossible to open one on a visa exempt stamp so you may find it easier to exit to a nearby country and apply for the visa there

Waiting for 2026 won't make any difference but you seem like a genuine tourist so should be OK, but as ever it will be up to the immigration officer you stand in front of

You need 500k baht for the application leaving around 400k baht savings. Nowhere near enough for the 5 years duration of the visa. Really they want to see ongoing income when they ask that question

@Maxim **********

you are not coming from Cambodia by land. The land border between Cambodia and Thailand is completely closed

@Michał **********

that's not what I asked. I can't help if you don't answer questions

If you have a residency permit you can apply in Qatar otherwise you will have to travel back to the country of your nationality if you really want the Non-OA visa. Otherwise you need to travel anywhere that will allow you to apply for a Non-O visa. Many won't issue a Non-O dependant visa for your wife at the same time as you apply for a Non-O based on being over 50 so she may need to apply for her own Non-O based on being over 50. She can't get a Non-O dependant visa inside Thailand nor any nearby country

Were you on an ED visa or extension of stay? If the latter have you cancelled it? And did you attend all the classes required by the school you attended?