If you wish to explore all "must see" features of Northern Thailand in no time, this route is for you.
First, we head to Chiang Rai to visit the famous Wat Rong Khun - Chiang Rai White Temple and a private museum Oub Kham, which is the best museum in Chiang Rai. Then we drive further and spend night near the Golden Triangle.
Then we visit the famous Golden Triangle, the point where borders of Thailand, Laos and Burma meet. Here we take a boat to make a small water trip along the great Mekong River. We visit Laos during this trip (since we visit only a border area, you will not need a visa for Laos). We also visit the famous Opium Museum (Opium Hall) that day, and drive to a border city Mae Sai, where we spend another night.
Next morning you have a chance to cross the border and visit a Burmese city Thachilek (no visa required for one day stay in Burma). Then we visit Queen Mother's Garden in Northern Thailand and go straight to Chiang Mai from here.

What to bring:  you will need your passport for Burma trip.
What you do not need: visa to Laos and Burma. We will visit only border areas where visa is not required.