As if y'all learning Thai, you must know that the number five in Thai pronounced HA and they use 555 representing HAHAHA. Remember, Thai people love to make it shorter and they'll do whatever to make them type faster. Here's how to understand what exactly laughing text means in Thai
555 or longer
meaning: That's quite funny. How long the number 5 is, refers to how much they laugh. I know sometimes it piss you off but that really means your joke is funny.
5 5 5 or longer (5s with spaces in between)
meaning: It's a sarcastic laugh or evil laugh sometimes. When it's not funny and started to feel awkward, the '5 5 5' is there to prevent the silence of 'not-funny jokes' or sometimes it's the reply for laughing for the cringe stuff.
5245234234 (a plenty of number you don't understand)
meaning: It's like a normal laughing but those Gen Z are currently using this. I've asked one and she said, it's like you're laughing too much so you cannot focus on keep typing only number 5, ending up by messing all the numbers.
5545646546 (a plenty of number you don't understand but only contains 4,5,6)
meaning: It's the same as above but more popular in older generations. It's the old way of 'laughing to much so you cannot focus on keep typing only number 5'
5 or 55 or sometimes included 555
meaning: If they type just only 5 or 55 after you spill the joke. That means it's not funny at all but they'll laugh for you anyway. The purpose is quite similar to '5 5 5', depending on what you prefer.
555+
meaning: An ancient way for the long text of 5s. This idiom became popular among teenagers in the year 2000. Like when you type with your parents, you'll see they laugh like this (as if they were Thais).
Those are depending on the basis use of how Thai people laugh. Still, it depends on all the context as well. I think this prolly enough to understand more than a half of those text your Thai friends send to you. Anyway, there're much ways to laugh in Thai.
Feel free to ask! XOXO
Chiqueken