I'm told this tradition started in Chiang Mai and has spread Thailand-wide; on special occasions, a paper lantern is sent sky-high. It is a tube of tissue paper attached to circle of wire at the open end. In the centre of this circle of wire is a smaller metal disc encased in what I think is fire-starter. It takes a while to get this white solid fully alight, but once alight, it burns for quite a while. So, the people celebrating, light the fire-starter, hold the tissue tube above the burning fire-starter til heat builds up in the tubular tissue canopy above, then let go. Provided enough heat has accumulated, the lantern lifts gently off and floats skywards, drifting in the breeze, visible for miles. The real beauty is when batches, dozens, or hundreds as at the festival of Loi Krathong, are released together. That's spectacular.