Thai writing was invented around the year 1283 by King Ramkhamhaeng the Great, who wanted his people to have a script for their own language. The shapes of many letters look a bit like Sanskrit and Khmer letters from nearby India and Cambodia, but rearranged.
One thing that is very different from English: in Thai writing, there are no spaces between words. A sentence is one long ribbon of letters. Children learn to spot where a word ends and the next one begins by reading lots of stories and saying them out loud, so the pattern becomes familiar.
Thai is a tonal language. That means the same sound said in a higher or lower voice can be a totally different word. The word 'mai' can mean 'new', 'silk', 'wood' or 'not', depending on the tone. To make this less confusing, Thai writing has tiny tone marks above the letters - little squiggles you can see, telling you exactly how high to say it.
Children in Thai schools learn the alphabet through a song that lists each letter with an example word - 'gor gai' (g for chicken), 'kor kai' (k for egg) and so on. It's a bit like singing 'A is for Apple, B is for Bear' - except it goes on for 44 letters and has its own tune.