To get high, most commonly by means of marijuana. Trees is a common slang name for marijuana. When you climb a tree, you're getting higher in elevation than when you were on the ground. Therefore climbing trees refers to getting high off of trees.
This pharse refers to moving up in rank within a particular field or business. If someone "climbs the corporate ladder" to the top, they started out at the bottom (stockboy, mail clerk, etc) and ended up at the top (CEO, CFO, vice pres., etc.)
Tim lived the American Dream. He started out as a desk clerk and climbed the corporate ladder to the top. He is now a CEO in the same field that he had started out in.
Climbing Thugs are climbing GANGSTAS. Those who refer to themselves as climbing thugs are those who spend all their time climbing because thats the THUG life = Climbing thugs will do anything for the sport, no matter how dangerous...even if it involves dynoing 50 ft in the air (only possible for CLIMBING THUGS) because we are the super heroes of climbing
Climbing thugs do the absolute most gangsta sport EVER. The peopleeveryone wished they were but some are...