1 2 3 4 worked as the default PIN today, Dec. 13, 2021, on my new AIS 1 2 Call SIM, that I bought two days ago. Thanks for the information!
I like to lock the SIM because I had a phone stolen once and the thief moved the load off the sim card to another account. If your SIM is registered to you, with AIS, and the SIM is locked, you can transfer the load to another SIM.