The 'where to base' question for Southeast Asia has a real answer if you think about it as a budget optimization problem.

Chiang Mai, Thailand wins on value if your priority is: low daily cost, good infrastructure, large expat/nomad community, easy language barrier, consistent internet for remote work, and a central location for regional day trips. You can live well for $700-900/month. The city doesn't have a beach.

Hanoi, Vietnam wins if your priority is: cultural immersion, excellent food, a base for northern Vietnam day trips (Ha Long Bay, Sapa), and lower prices than Chiang Mai on food. The city is denser and more chaotic than Chiang Mai. Daily budget: $22-28.

Phnom Penh, Cambodia wins for: the most extreme budget available ($15-18/day is genuinely achievable), a smaller expat community that isn't oversaturated, and a base for Angkor Wat day trips. The city is rough around some edges but improving fast.

Penang, Malaysia wins for: the best food in Southeast Asia at reasonable prices, strong English, excellent transport within the island, and a comfortable mid-tier between Thailand budget and Singapore costs. Daily: $30-40.

My current recommendation for first-timers: start in Chiang Mai for 2-3 weeks to find your feet, then move based on what you discover you want. The infrastructure in Chiang Mai is forgiving of beginner mistakes.