Are airlines particular about carry on dimensions?

I'm flying from Singapore to Chiang Mai on Scoot. The dimensions given for carry on on their site says 54cm x 38cm x 23cm (total linear dimensions can't exceed 115cm). I recently bought an American Tourister luggage dimensions of 50 x 39 x 25cm (total linear of 114cm).

Am I likely to get turned away for having my carry on too thick? I'm just afraid they might ask to put my luggage in a frame. It may not fit due to width but it still fits their total linear requirement.

Help! Should I return my luggage purchase?

Added (1). I'm wondering if there's anyone who's been on scoot who has experience with this kind of problem. I'm wondering why they included total linear dimensions in their sizing: /

The airline itself is likely to be able to give you the most accurate information. Why not call them?

The dimensions given for carry on on their site says 54cm x 38cm x 23cm (total linear dimensions can't exceed 115cm).

. I recently bought an…

CAN YOU COUNT

You can read.
Think is 39 bigger than 38?

It may not fit due to width. So what is your question?
If it fits it fits.
If it does not fit you pay extra and it goes as a checked bag.
OVER IS OVER is that a real hard thing to understand?
If you item has SOFT sides in might squeeze in. You are not required to stuff your item to bursting capacity.

The store might take it back. THEY DO NOT HAVE TO.
The Airline Agent you deal with MIGHT NOT require the item to go in the size checker.

OVER is OVER if caught with an over size item YOU PAY EXTRA.
The other passengers are also trying to take extra too. Some extra weight a really big purse, wearing five or six layers of clothes or whatever.
It costs the Airline to haul stuff. They want to be paid.
They get money from the seat and extra luggage fees for extra luggage.
What is it you do not really understand?

Millions of other passengers want some extra too. Shall we load all their stuff first? If there's no room for yours you can then complain about the others using "your" space.

The overhead bin door needs to close. There's only a certain amount of space. Your item fits or it does not.
If it fits you have no problem. If it does not the On board crew will have it re tagged as checked luggage and charge you accordingly.
You have proven that you can read the requirements.
Understanding them is not really that difficult.

You need to think. The luggage bin is like a box. It has to close the width is part of this. IT MIGHT FIT It might not.
ALL four measurements count The Height, the width the length. And the total of all three.
As your bag can be turned on its side changing its height it MIGHT FIT NO GUARANTEES.
It all depend on all the other bags stuffed into the bins before your bag gets to one.
Hard sided bags are harder to fit. Those with soft sides like a duffel can change their shape and fit easier.
If the luggage bin is full IT IS FULL, Just the way it is on some flights.
At that point an oversized bag will be charged extra.

Your bag MIGHT FIT and there's no issue. There are no GUARANTEES.

Before you get to the airport, make sure your cabin baggage does not exceed the permitted allowance, or you'll be advised to check in your baggage at the airport and be subject to excess baggage fees!
You have been warned.

The Airline likes to make money. One way is charging baggage fees for extra large bags,
It might pass it might not. If it passes no issue if it does not YOU PAY extra.
A soft sided bag will squeeze to fit if you do not stuff it full.

It may not fit in the overhead compartment. So it may not be just an arbitrary rule.

Airlines can be strict on occasions and at other times let things go depending on how busy they are, whether they like the look of you etc. The thickness is the trickiest thing. Is the bag soft enough to squeeze down to 23 cm if necessary? If it sticks out of the top of the gauge by 1 cm that isn't likely to be an issue. Whatever you do don't ask if the bag is OK and don't try it in the gauge without being asked - I've actually seen people do that drawing attention to the fact that their bag doesn't fit. I thought Chiang Mai is Singapore so how can you fly from Singapore to Chiang Mai?

Yes, if it does not fit under the seat or in the bin they will make you check it. But it has to fit through the security deal first, so odds are that if it fits through that, then it will fit in the overhead. The only exception to this is airlines like spirit that get really picky as they like to charge fees for carry ons