@Alex ************

Single Entry visa has nothing to do with the requirements of extending the period of stay you got on entry with this visa based on following an education or internship.

Strange that you're enrolled in a 6 months internship and the school can only provide a 3 month stay, what is the reason why you can not extend?

Alternative is go to a neighbor country and apply for a Single Entry Tourist Visa which gives you 60 days on entry and can be extended once on basis of tourism with another 30 days

The Visa is a personal item, which means each of you has to meet the requirements on their own.

You might look into a Non Immigrant O or O-A for one of you where the person must meet the financial requirements and for the married partner a Non Immigrant O as depending on the partner without financial requirements.

As long as you enter before the valid until/enter before date mentioned on the visa, you get maximum 1 year of stay OR until the valid until date of your health insurance, which ever comes first.

@Tullio ******

That depends on what kind of stay she has, best is to ask that directly to your local Immigration Office.

Until 15 years of age, minors will not be financially fined, after 15 years until 18 year they will be financially fined but do not get blacklisted due to overstay.

As she is 17 years, she will be fined for overstay but not blacklisted.

You might try the Extension of Stay based on being unable to travel but with all restrictions getting lifted, make a plan B like short trip abroad.

The truth never hurts. But you might write down you are unable to travel due to covid contaminations world wide, or just I like to stay inside Thailand.

I have been told, BUT what date is mentioned on the stamp inside your passport ? If that date is 6th July you have to go back on that date to the Immigration Office OR stamp out the country on or before that date to avoid being in overstay.

If you fly out on the 7th early morning, check in and stamp out late night on the 6th.

@Rene *****

I know that the Non Immigrant O visa where O stand for others has many reasons, that is why the Embassy always put a small stamp like "Thai Wife"on the visa. As this e-visa is new I like to see how the reason as you mentioned "Thai Wife"and the reason depending on foreigner with long stay are mentioned on your E-visa.

Can you send me a copy of that description, you can use PM if you like but blank out the personal details.