@John ********

When you apply for a visa, normally you only submit the page with personal data, not the stamps, so it will not make any difference to have a new passport when you apply for a visa.

At immigration they also have all history info, but I can imagine that a quick look at a passport full of Thai stamps can be an extra trigger to check, but that is only when entering the country.

@Stéfan *******

In this case the visa was not denied, they just corrected the type requested to the type needed.

@David *******

It is not uncommon, more countries practice this and warn before that difference in fees will not be refunded.

A visa should match with what your reason is to visit a country, it is not a kind of entrance ticket you buy for a certain period, and then gives you to do what you want in a country.

@Stéfan *******

That is your opinion, but it is also the responsibility of the applicant to choose the correct visa. When you select wrong visa, they can correct you, or reject the application. I think the correction is much more customer friendly.

@Brandon ***********

That is the only correct answer, immigration not transfers visa, they only can transfer extensions of stay.

@Stéfan *******

If you not choose the best visa for you purpose of stay, they sometimes give you the most appropriate visa.

@John *********

saying nothing about retaining means it should be retained the whole period.

If it was allowed to let it drop, it would be described as with non-o retirement.

They will only check if they for some reason suspect you, or just coincidental because they might need to do a certain number of checks in a certain time.

@Christopher *******

The visa requirement is a requirement during visa valid period, not just for the moment of application.

@Siggi ******

There certainly is a legal base to ask, it is one of the requirements for DTV visa.

Every visa holder can always be asked to show they still comply with visa requirements.

That is not only in Thailand, but everywhere in the world. A visa is never a document that gives you right to enter a country without checks.

Normally they will not check, but if for some reason they want, they can.

@Heath *******

When you comply to the visa requirements the in country extension might be the best way to go. When you do not comply anymore doing a bordebounce yourself might have the risk questioned and checked for funds and documents, unless you pay.