I switched over to
Line Mobile in January and never looked back. Anyone can register for a sim card, completely online and it's delivered in 2-3 days. Rates are significantly cheaper than the other prepaid options, and even if you go with the small 5gb plan, once you go past that, it's unlimited 3G. You also get a 10% discount when paying your bill through Line Pay, but foreign credit cards work just fine.
https://th.linemobile.com/en/r/r3mvkv