Tired of asking for the Wi-Fi code at every restaurant or bar? Then buy a local SIM card for your phone. You can get SIM packages at any 7-Eleven, but you’ll always need to show your passport. The catch is that 7-Eleven is only allowed to sell you tourist packages, which are more expensive than regular ones. For about 350 THB, you can get a 30-day package, but it’s for internet only — no calls included. So sometimes you’ll have to visit a few 7-Elevens before finding one that will sell you a regular SIM. If you spot one of the small phone shops around town, they’re more likely to sell you a regular SIM.
If you only have one SIM slot and put a Thai SIM card in it, you won’t be reachable by calls or SMS on your Foreign number anymore. That’s not really a big deal — I mean, who even sends SMS these days? And getting calls can be really expensive. The good news is, with a Thai SIM card you can still be reached on your Foreign number via WhatsApp.
(*) Speaking of SMS, some websites still use them to verify logins from strange locations. Consider bringing your old Nokia as a second phone with your Foreign SIM card inside. The bonus: no one’s interested in stealing an old Nokia, so you’re less likely to get into trouble if you lose that SIM card.