The main difference is that 101 Okey requires a 101-point opening and deals 21 tiles, while classic Okey deals 14 tiles and has no opening requirement.

In straight Okey you keep your groups hidden and go out in a single move. In 101 you must first lay melds worth at least 101 points (or open on five pairs) before playing tiles, then lay off and finish. Scoring also differs: 101 uses a points system where low totals win and the finisher scores minus 101. The ace is low-only in 101.