Is roaming free in Thailand with my home SIM card from the US or UK?

It's highly unlikely that roaming would be free in Thailand (or most of Asia) with a standard SIM from the US or UK. Unlike within the EU, there isn't a 'Roam Like at Home' policy for most international travelers in Asia. Major US carriers like AT&T or Verizon, and UK providers such as Vodafone or Three, typically charge significant daily or per-MB roaming fees. These can quickly add up, making an EastESIM a far more cost-effective and predictable solution for staying connected across Thailand, Vietnam, or Indonesia.