Zoe in Yellow occupies a corner of the old city's main bar area, near Ratchaphakhinai Road, and has been drawing backpackers and budget travellers for years. It's an open-air affair: plastic chairs, cheap beers, local bands playing everything from reggae to Thai pop, and a convivial chaos most evenings from about 9pm.
The drinks are cheap, the vibe is unpretentious, and it fills up without effort. Several other bars operate in the immediate vicinity — the whole block functions as an informal nightlife cluster within walking distance of most old city guesthouses. Not glamorous, but genuinely fun.