Mahidol University's research reveals GenAI is fundamentally disrupting brand loyalty in Thailand. Key findings: 82.4% of Thai GenAI users consult AI weekly; 56.2% are willing to switch brands based on AI recommendations, though 60.6% gain higher trust in existing brands when AI confirms their quality. AI platforms (ChatGPT 95.2%, Gemini 76.4%) influence purchase decisions most heavily in apparel, home goods, and food categories. Younger consumers (18-24) show highest AI influence (67.2%). The research introduces a "SWITCH Framework" to help brands adapt marketing strategy for the GenAI era, signaling that future brand loyalty depends not just on reputation but on what AI "knows, believes, and recommends."