Located north of Chiang Rai, Mai Sai is the most northern town in Thailand and directly on the Thai-Myanmar border. As this is one of the few active crossings between Thailand and Myanmar, Mai Sai has a 'border town' feel about it - plenty of coming and going and plenty of activity. The main street acts as a night market but most stalls close before it gets dark. The town has an excellent opium museum at Sop Ruak and is famous for its gem market where you can find precious stones such as rubies, emeralds and jade (all mined in Myanmar). There's a parallel market on the Burmese side of the border where gems and a host of other goods (mainly from China) are sold. A particular favourite is Chinese Champagne - huge magnums of the stuff come in at only a couple of dollars! Foreigners are allowed to go into Myanmar through Thakileik and can reach as far as Kentung. Don't expect too much from Mai Sai - this is not a cold war checkpoint, nor is it a wild west-type town. It is though a great place to visit and to get a taste of Myanmar.
Details: To cross the Myanmar border you will require a passport. A day pass into Myanmar costs around $5. Admission to the opium museum is 20 Baht.
How to get there: Buses leave Chiang Rai for Mai Sai around every hour. The fare is 20 Baht for a regular bus and 40 Baht for an air-conditioned bus.