I  came to  Thailand on Non Immigrant O Visa,  intending  to change to Retirement after 60  days.

I  have just  watched video on  youtube  which gave different days of when to apply.

Anybody know     THANKS

You are already on the retirement non-O, so you cannot change to it.

You can apply for an extension based on being over 50.  At all immigration offices you can apply when you have 30 days or less left.  At some immigration offices you can apply when you have 45 days or less left.

 

That is usually not the factor that matters.  What matters is that you need to be able to show that the required funds in your Thai bank account have been there for 2 full months already at the time you apply for your extension. (Unless you're using an embassy letter for proof of income)

35 minutes ago, kevtheblue said:

I  came to  Thailand on Non Immigrant O Visa,  intending  to change to Retirement after 60  days

So you have a 90 day stamp. 

You mention wait for 60 days. 

You must have a Thai bank account in your name only and plan to season the 800k for two months. 

If all that describes your situation you can apply up till expiry of current stamp. 

Do not do that. As soon as funds seasoned then apply for extension. 

At certain Immigration offices you can apply 45 days in advance, and at all Immigration offices 30 days in advance of the 90 days.
In all cases you must have 800K seasoned in a Thai bank account for 2 months prior to the date of submitting the application.

 

When you apply depends on if the funds were previously deposit in a Thai bank account, or whether you just deposited the 800K after arrival.