Vexillology

Current flag for reference:

Wikipedia article about the flag

Back before the current flag, Siam used a red flag with a white elephant:

Legend has it that the king, to his horror, encountered one of these flags upside-down, and to avoid that from happening again, decided to change to a flag that could not be turned upside-down. As a consequence, the following flag was adopted in 1916:

As you can see, the blue field was red back then. Allegedly it was changed to blue to show allegiance to the Entente powers during WWI, since they had blue-white-red flags. Alternatively, blue was associated with Friday, the weekday the king was born. Or alternative to that, blue just made the flag a lot prettier (which it indeed does).

Wikipedia article about the flag

The flag is very similar to the flag of Syria and Iraq, which had similar Arab nationalist regimes. In fact, for a time, the three countries had flags with one, two and three stars respectively!

North Yemen:

Syria:

Iraq:

Before the coup, North Yemen was a monarchy, and its flag also looked much like what you could expect from a Muslim monarchy. Compare with Saudi Arabia for example.

The presence of Angkor Wat has been remarkably stable across the various flags. It also makes the Cambodian flag on of the only four state flags to feature a building. The other are the flags of Portugal, San Marino and Spain.

Wikipedia article about the flag

The George cross is indeed a British military award, that Malta received in 1942 for its bravery in WWII.

Wikipedia article about the flag

Nevis, the smaller of the two islands, also has its own flag:

Wikipedia article about the flag

This flag won a nationwide poll in 1949, but some changes were made to it afterwards, leading to the Malaysian flag we know today. The reason for these changes seems somewhat unclear, more than that the politician Onn Jaafar suggested them.

The proposal was inspired by the flag of the Malaysian state Johor:

Source: Wikipedia

The previous flag was very similar, but with 11 stripes and an eleven-pointed star:

Unsurprisingly, the stripes and the points of the star represent the constituting states. Since the number of states had grown to 14 in 1963, the flag was updated accordingly. Only two years later, Singapore seceded from Malaysia, but they decided no to bother with changing the flag again.

Source. Made by Regicollis.

Wikipedia article

They even have their special national anthem to represent the entire island: Ireland's Call

Article about the adoption of the flag

Wikipedia article about the flag

Here's a painting depicting when Kim Il Sung selected the new flag (presumably a very objective depiction and not at all idealized for propaganda purposes):

Note the two other proposals to the left:

The six points of the Commonwealth star represented the six states of Australia. Later, a seventh point was added to represent the territories.

The reception of the flag was mixed, and it remains debated til our days.

The Argus newspaper reported the following in 1901 about the new flag:

In years to come the flag which floated yesterday in the Exhibition building over Her Excellency the Countess of Hopetoun, who stood for Great Britain, and the Prime Minister (Mr Barton), who stood for Australia, will, in all human probability, become the emblem upon which the millions of the free people of the Commonwealth will gaze with a thrill of national pride."

Alternatively, the then republican magazine The Bulletin labelled it,

a staled réchauffé of the British flag, with no artistic virtue, no national significance... Minds move slowly: and Australia is still Britain's little boy. What more natural than that he should accept his father's cut-down garments, – lacking the power to protest, and only dimly realising his will. That bastard flag is a true symbol of the bastard state of Australian opinion.

Wikipedia article about the flag

Notice that the diagonal stripe goes from the top left to the bottom right, unlike most other flags with a diagonal line (DRC, Namibia, Republic of Congo, Saint Kitts and Nevis, Solomon Islands, Tanzania). Brunei, however, also has the stripe in this direction.

Wikipedia article about the flag

As of today, Angola still uses this flag, with a machete as a fairly unique feature:

The pattern in the new proposal is inspired by rock paintings at Tchitundo-Hulu.

Info about the proposal

Brasília is of course a city characterized by its modernist design and architecture, and its geometric layout, so its not more than logical that the flag has a similar feel to it.

The flag was designed by the poet Guilherme de Almeida. The Cross of Brasília in the center symbolizes the indigenous heritage and the strength that hails in all directions. The white background of the flag stands for peace, and gives the idea of infinity, or the vast Brazilian territory. The green and yellow colours in the middle refer to the most commonly used of the four colours of the national flag to represent Brazil. The four yellow arrows symbolize the native nations of Brazil, whereas their pointing into the four cardinal directions of the compass stands for the centralized emanating political power of Brasilia, as the capital of the country. The yellow arrows also form a cross, which symbolizes both the Southern Cross. With their feathers, the arrows form a lozenge in the middle, a reference to yellow lozenge of the national flag.

Before 1969 this design was used:

Wikipedia article about the flag