ABCDEFGHIJKLMNOPQRSTUVWXYZ

You are finding 3 places.

Also, Kiribati's flag is for checking if you got the "places" correcct.

Hint 1:

Kiribati's flag has water in it. Its useful.

Hint 2:

Fixed version:

Hint 3:

What does Azerbaijan and the Netherlands have to do with water?

Hint 4:

Think of elevation.

Last hint:

If Bolivia, Ecuador or Colombia was pointing to Kiribati's flag, It would be on top of the image.

I've got the countries figured out, but there's five of them (six including Kiribati), not three:

• Big flag on the left:

KIRIBATI (I haven't even spoilered this since it's mentioned in the question).

• Flags on the right:

AZERBAIJAN (internet domain .AZ, calling code 994)
NETHERLANDS (internet domain .NL, calling code 31)

• Mottos below:

TUVALU (internet domain .TV, calling code 688). National motto "Tuvalu mo te Atua" = "Tuvalu for the Almighty".
SURINAME (internet domain .SR, calling code 597). National motto "Justitia – Pietas – Fides" = "Justice – Piety – Trust". Interesting that only the last two-thirds of this is included; that must mean something, but I'm not sure what.
TURKMENISTAN (internet domain .TM, calling code 993). National motto "Türkmenistan Bitaraplygyň watanydyr" = "Turkmenistan is the motherland of Neutrality".

Possible method of answering (especially given the title):

something to do with the two-letter internet domains for these countries. Interestingly, Kiribati (.KI) is exactly a 3-letter Caesar shift from the Netherlands (.NL), but between them is not Azerbaijan but Macedonia (.MK). Meanwhile, Tuvalu is .TV and Turkmenistan is .TM.

By the way,

what I've got as Tuvalu could also be indicating TOKELAU (motto "Tokelau mo te Atua", but a territory of New Zealand rather than an independent state).

• Could "piety trust" hint towards "in god we trust"? Dec 3 '21 at 12:20
• You got "a translation of something" though Dec 3 '21 at 12:36
• @LukasRotter I was thinking of that too, but it seemed too tenuous a connection, and there's a whole load of countries with national mottos equally close as "in God we trust" to "piety - trust". I was also thinking of this one, mostly because it's close to a couple of the other places featured. Dec 3 '21 at 13:47
• Fun fact: About 10% of Tuvalu's entire GDP comes from leasing .tv domains. Dec 3 '21 at 16:06
• (Minor note: The first word is missing from all mottos -- only that it's the country's name in two cases. I'll also note that both sn and tv have something in common with the flag of Kiribati.) Dec 3 '21 at 17:03

[Not a full answer, only some loose thoughts that are too long for comments. I'm building on Rand al'thor's answer here.]

Flags

The flag of Kiribati features sine-like waves and a bird over a rising sun. Kiribati is an island state in the Pacific Ocean. Its territory (Mostly "aquatory", really) is known for spanning both the equator and the antimeridian, but not the international date line.

The small flags to the right (Azerbaijan and the Netherlands) point at the sea. Azerbaijan's capital Baku is the lowest capital of the world. It is on the shores of the Caspian Sea, which is 28 m below sea level. Parts of the Netherlands are also below sea level, in particular the inland bay of the IJsselmeer.

We are told to check the "three places" with the flag of Kiribati. A wavy version of the Dutch flag can be seen near the horizon of Kiribati's flag. Some of the flags of Dutch provinces, notably Zeeland and Overijssel, but also the polders of Flevoland, have wavy designs. The city arms of Baku also feature waves, but they are not sine-like, but pointy.

"Mo te atua"

Tuvalu mo te atua is the state motto of Tuvalu, an island state in the Pacific Ocean and nor far from Kiribati. What's interesting is that Tuvalu's coat of arms features a wave design like the one in the flag of Kiribati, albeit in gold and blue.

"Poety - Trust"

Justitia – Pietas – Fides is the state motto of Suriname, whose coat of arms also features waves, this time in white and silver.

Ecuador, Bolivia and Colombia

The last hint mentions that those countries would refer to the top of Kiribati's flag. All three have coats of arms with a condor sitting on top of a shield, so like Kiribati's flag, they have a bird near the top. They are also in the Andes, which makes them places of high elevation. Bolivia is landlocked, but Ecuador and Colombia have sea coats, so they have points at sea level. (According to this list, they don't have significant points below sea level, though.)

Bitaraplygyň watanydyr

Türkmenistan Bitaraplygyň watanydyr is the state of Turkmenistan. Like Azerbaijan, it lies on the Caspian sea and therefore has parts below sea level. Unfortunately, its coat of arms has neither waves nor birds nor sunrises: Among other things, it features the crescent of Islam and the former president's pet horse ("a source of pride to the people of Turkmenistan") in realistic, not heraldic rendering. (But the country's second largest city Türkmenabad features some waves in an Islamic shield.)

ABCDEFGHIJKLMNOPQRSTUVWXYZ

That's the title. Surely it hints at something. I have no idea at what. (But I note the A–Z and that Azerbaijan's two-letter cpountry code is AZ. Rand has already pointed that out, too.)

You are finding 3 places.

We are looking for unspecified "places", so not necessarily countries or towns. I think that none of these places is a country mentioned so far, because its flag or motto is in the question. My guess is that we are looking for three places that share some characteristic with the countries already shown.

So far, we have seen a hodgepodge of rather heterogenous characteristics. Some proposals:

The British Indian Ocean Territory is the prime example for wavy water in heraldic designs. It is not the only place with waves in its coat of arms, though.

The Dead Sea is the Earth's lowest point on land and like the Caspian Sea and the IJsselmeer it is a body of water below mean sea level. In this puzzle, countries seem to be categorized by their lowest point. If that is below sea level, they are associated with the waves in Kiribati's flag, otherwise they are associated with the sky.

I can't think of a third candidate, which will probably be identified by a third characteristic. Perhaps it's just Mount Everest as the highest elevation or, more likely, Lesotho, which is the country with the highest minimum elevation.

But that doesn't account for A–Z or Turkmenistan. Well, I'm out of ideas.