When you can't write out okay, just write O.K.
If that is just too much, write K.
If you really, really mean OK in a big way, write KK
Just never write KKK , cause that's bad.
Since I am totally uncool, I write OK in messages.
K seems silly to me.
And maybe a wee bit lazy.
I really don't understand shortening a word that has already been shortened to two letters.
OK, maybe if you were doing Morse code and had to do all those dots and dashes.
But, if you are using a keyboard...